Its not hard. I covered the entire front 6-8 inches of my roof with painters tape and took the measurements from here and made my own template. It made it easy to measure, check, measure, check, check, measure, measure, measure, check, drill. Also, having the tape there makes it easy to prevent the drill bit from scratching the paint.
I started with a really small bit, then went up to the size needed for the bolt so it wouldn't slide around.
The wiring is not in the headliner, but the plug for the harness is just to the right of the passenger side footwell right behind that plastic peice. This and there are holes in the metal brace in the front of the roof for the plastic push pins that hold the harness up there so its simple. pull the a pillar plastics off, pull the headliner plugs, then slide it down out of the way.
buddy of mine had mine done in just over an hour with me being very anal about everything that involved drilling or cutting my truck.