Im going to cater more to 99-07c in this post - its all i know at this point, but its good basic info for many setups.
First of all it really depends on what you want. The big decision is whether or not to go electronic air management, im sure youve checked them out and know what they are all about - and for something you want to enjoy driving daily, id recommend one, the prices arent too outrageous these days. I initially had a non-electronic air management setup and didnt enjoy it, I want everything to be perfectly precise and level (im anal about that stuff), and i had trouble with that with individual valves and a switchbox - im sure you could make it work, many have, but i had difficulties. I had other problems due to installer error, which is another reason id recommend electronic - most come with valve bodies and other things that reduce install difficulty and possibilities of future breakdowns, leaks, and maintenance. Like stated previously, thousands have had perfect experiences with non-electronic setups, so if you are operating on a budget and thats your game - play it well, ill give you some tips:
WELDING/FABRICATION WORK: I would surely pay someone to do the welding/fabbing if you are not 100% confident with it.
-Rear link setup:
Tri-links and 4-links are the best setups on these trucks, get a reputable shop to build and install one of these. Bolt on kits are tempting because of saved install costs, but do your homework and see of you save money having someone build/install one for you. A link setup inside the frame rails will take alot of relocating and cutting/removing. A tri-link will need to be inside the frame rails. Many 4 links are as well, but its not absolutely necessary, so i would go this way for a budget build so you dont have to get a fuel cell or different gas tank, and relocate other things between the frame. A 4 link rides great, and has minimal side-to-side axle movement with a watts link when dropping/raising , and minimal to no front to back movement when built well. I bought a used KPcomponents 4-link for a good price, and have enjoyed it, but I would not have paid their ridiculous retail price, research on who will build what for you and for what cost - i cannot help you much on the cost element here.
-Notch, Bed, etc:
Get a reputable shop to do the notch, go check out their welding and frame work beforehand IMO. Do not buy a notch kit from an internet shop, anybody reputable shop should be able to fab one up for you. I would recommend setting up for the biggest tire you would even run, you dont want to be limited by your notch if you want to step up wheel sizes, but you dont need an oversized notch either. Make sure they box the frame on and around the notch, and add bracing between the notches for extra strength. My notch was done by a local shop for $250 and It is holding up fine after 4 years. The notch cover in the bed can be done many ways - I leave the style up to you. I went with a ThorbeckeBros steel rounded cover setup for 24in tires (the size my notch is setup for). It does its job, but if i did it again i would cut up another trucks bed floor and make my notch match the rest of the bed from that material - that gets pricey though if you arent doing the labor id imagine. My notch was bought and installed for $400. I havent tubbed the front yet, and dont plan to do so for awhile, so i cannot comment on price here. The gas tank will need to be raised if it is left in the stock location. The method to do this is to notch the bed first (you arent cutting into the cab, just removing extra material), then raise each tank mount bracket 1.25in. You will not drag with it raised this way. I had a friend do this for me so I cannot comment on cost. You will also want shock relocators for the front suspension. This aids with the ride quality; it keeps the front from feeling like its riding out a cloud and keeps the truck feeling as close to stock handling as possible while still allowing the truck to lay out. A shop quoted me $250 to build/install one for me. Someone (possibly you) will have to do some cutting on the front suspension as well. The spring pockets need to be cut to clear for the bag, and the bump stop and its mount will need to be cut out (for 99-02 iirc). I did this with a dremel, wasnt bad.
Add it up: 250+250+100(gas tank raise estimation)+400 = $1000est. I believe I got a decent deal on labor, was done at a friend of a friend's shop so he helped me out a little plus i got alot of work done there- then again who knows if he gave me a deal or not. Could cost you more, this thread is all just estimated cost.
PARTS RECOMMENDATIONS: Simple recommendations, with justifications.
-Compressors: Go with two. Simple. A fullsize truck takes ALOT of air to drop/raise its weight, and even a 5gal tank takes around 4min to fill from empty with two compressors. One compressor simply isnt enough. (This is all null and void if you go for a high dollar oasis or something that can flow crazy amounts yet costs crazy amounts.) I use and am very happy with my 2 Viair 360c's. They have never seized on me, fill fairly fast, dont use gobs of electric power from your alternator, can be rebuilt, and are somewhat quiet. Also, they are rated at 200PSI, many are rated at 160PSI - you want the former, more air = better. Also keep in mind that your pressure switch will also need to be rated to match your compressors (i.e. 200PSI), they are easily attainable. I got my compressors used as well, but a new set goes for $400-ish without tax/ship, the pressure switch can range from $5-$25 - you get what you pay for.
-Air Tank: Go with 5-10gals, can be had in many variations, just know what you need for your setup. $100ish?
-Switchbox: DONT CHEAP OUT HERE. Research, and remember if this dies...your air setup dies. I got a switch box from SD.com. Get a rocker box IMO. $50-$100 here.
-Valves: Get 8 dude, please. You want to be able to control all 4 bags on your vehicle, its safer, is easier to make ride better (dont have to add check valves everywhere, etc), and you can level your truck easier. I initially rode with 8 SMC 3/8 valves, worked well, didnt have to have any drop/fill controls to help with their speed - but i wouldve liked to slow down the drop a bit, just personal preference. I got these used, but new I think they still go for around $50 a piece, so $400 here.
-Fittings: Use Brass. I prefer PTC (push to connect). They are way easier to install/uninstall, airline leaks are easier to repair once driving, and they leave less room for leaks. They are pricier, but are way worth it IMO. I think i spent around $125 for all of my fittings, check valve, misc stuff, cant remember exactly though.
-Relays, electrical, etc.: I used a Stinger 80amp relay, they are about $25, but are better quality than the 10amp 2000cycle ones you buy from walmart. They are meant for this type of thing and make install a snap. Use a good stranded wire to wire anything, always follow install instructions when referring to gauge size, etc. Always loom when you can. Also, the stinger relay recommends a large gauge wire to operate the compressors; I used 1ga amplifier wire. Around $75 here, alot more misc stuff goes here than you think.
-Airbags: Id get 5, one extra, for piece of mind, just sayin. Do your research here and find one that gets good reviews and is in your price range. The less air it takes to fill it the better it will ride and easier it will be on your air consumption. I use Firestone 2600's all around and really like them in the rear, they arent awesome in the front - but I havent added shocks yet, so that could all change when i do so. Around $200-$300 here for a decent sized/quality bag.
-Front bag kit: You can use cups up front, KP makes a good set that can easily be modified and installed, its pretty much bolt on. They go for $150 +tax/ship nowadays. Many other kits are available, none as cheap as cups, but most yield better results.
-Gauges: There are so many options here, I went with simple KP gauges along with a 3-gauge pod. Worked fine. Youll need three for this, 2 of which will need to be dual-needle in order to read 2 bags, one to read your tank pressure (or another dual needle if you run two tanks). 1/8 airline and the appropriate fittings will also be needed, be sure to get enough. Again, got all this stuff used, so just to estimate id throw in another $200 for gauges/pod(s).
-Misc: Dont forget the stuff that nickels and dimes you if you do it yourself, tools, nuts, bolts, screws, beer, band-aids, stuff you break, etcetc. Throw in another $200 here just to be realistic.
-Spindles: Do you have spindles, you didnt mention it? If not, get a set of McGuaghys 16in+ and slap them on there, they give you the best angles throughout suspension travel on these trucks, most places retail these at around $250.
-Shocks: Again, so many options here, do your research, but your stockers wont work. Nother' $200 here for cheapies.
Add er' up: $2450. Sounds about right to me.
So there ya have it. Once its all said and done Id estimate you spend 4k on it after shipping/tax on everything. This price is doing all of the non-fabrication labor yourself.
I can add more on Accuair later. They can be cheaper when taking into account the cost of all the small things in a non accuair setup, plus often come with kits including other necessary parts, but more on that in another post or edit. This is a huge job, labor and pocketbook-wise. Dont underestimate either aspect, I did, and ive paid dearly (and still am), but I sure have learned alot in the process. Learn from my mistakes, thats why we are all here.
Let me know if you have any questions or want to add any info,
Brandon