Thanks all for the kind words. I will add a few pics of the project, I think it will answer your questions better than I can explain.
1- I popped out the 4wd switch to make sure I wasn't going to cut or drill into anything behind the plastic. Once I determined it was safe, I set the 4wd switch back in place so I could measure and sketch out my cut lines on the painter's tape:
2. The dimensions of the in-dash mount (the part of it that fits into the dash) are 1.5" wide x 2.25" tall. I made my lines slightly smaller than that so I could file off just enough material to get it in but it is so tight that I don't need any other adhesive to hold it in place. I measured, remeasured, eyeballed it and tweaked it until I was happy it was centered side to side and sat close to even with the 4wd switch up and down. There is no perfect because the dash is neither square nor flat; you just have to get it where it will make you happy. Once I had it where I wanted, I drilled my corners out with a 1/8" bit:
3. Then I Dremel'ed out the rough hole, with about 1/16" material left and the corners to be filed out:
4. Once it was about 95% cleaned up, I took off the painter's tape and made small adjustments to the hole with an exacto knife and a square file, constantly test fitting the mount. Here are a couple of pics of what is behind the dash in that area, notice the objects at the bottom of the hole and to the right side in case you want to mount something larger than 1 1/2" x 2 1/4":
5. Once my hole was done, I shop-vac'd and wiped everything down, ran my cable from the PCM up to my hole, and plugged everything in:
I hope this answers any questions. I have a bunch more pics but these tell the whole dash story. Let me know if you have any more questions.