There's not a whole lot of cutting involved.
Make sure you don't go too cutting crazy, there's not much room for that, as your projector will hit the core support.
You have to find the happy medium for the depth of the projector. Not too far up against the lense of the light, not too far back into the core support.
Be patient, use a dremel, and do lots of test fits by setting the lense on the light for that depth, and lots of walking out to the truck and fitting for the rear depth.
Actual difficulty, I'd say 6/10.
Once you set your projector in the housing, it'll click in your head and you'll know what to do. You're going to dremel out a batman logo more or less until your projector fits flush. It'll all fall into place.