There will be some very minor trimming required to the area behind the dash panel. I bought a dremel tool just for this, and used a small cut off wheel tool with it. (don't know how I made it all these years without a dremel!) I trimmed about 1/4" square off the female area that the trim panel clip nearest the lighter used to go into behind the dash panel.
I found it was easier to remove the entire dash panel and work on it out of the truck. All you need to do this is remove the screw behind the bag hook, open the cupholder and ashtray, and then pull down on the knee blocker below the steering column. The knee blocker will open up then, allowing you easy access to the edge of the dash surround below the lighter. Just pull it towards you and then work your way around the panel removing the clips from their sockets. Unplug all the electric connectors for the climate control etc; and then the dash panel will be removable.
Before starting to make a hole, I also removed about 1/2 of the plastic on the male portion of the clip below the lighter that is attached to the removable dash panel to allow enough room for making a hole.
I ran my 2" hole saw through a piece of wood first, and then clamped the wood with hole in it to the dash panel. This allowed the bit to start cleanly without the benefit of a pilot hole. I cleaned up around this opening a bit with the dremel, and that was enough for the gauge to fit snugly within the opening.
I got power for the gauge controller box from the former lighter plug. Also, the two screws directly below the radio seem to be a very good ground for lighting.
Let me know if you need any other help or clarification.