Seems like it is going to be easiest to just order a harness from nelson or BBP.
Do i have to change the alternator also? Or is that just recomended?
If you have the 105amp alternator, I would replace it with a 130amp or 145amp. My 130 amp just barely keeps up. But I also have a LOT more electrical stuff than you, along with rear AC. So you should be fine with a 130-145 unless you have a monster sound system.
And if you dont wanna pay $100 for a harness, send me those fan pigtails and I can make you a harness for pretty cheap.