The steps in this thread are very good, and I just replaced my switch using these instructions. Taking out the left side vent and the headlight switch really opened things up and let me see. I was able to do the entire job without crawling under the dash with the exception of putting back on the AC vent tube. I used this 33 piece precision screwdriver set from harbor freight:
Precision Screwdriver Set - 33 Piece
http://www.harborfreight.com/33-piece-precision-screwdriver-set-93916.html
It has a long flexible extension arm where you turn the base and the tip turns. And it also had the right size torx bits as well as a tiny flathead attachment for this job.
Here is a picture. It is kind of blurry so I outlined it in white. For loosening the set screws I was able to do it through the ac vent, and for tightening them back a reached under the dash. (If I were to do it again I would go under the dash both times as it was easier)
The hardest part of the job was trying to get a flashlight to point so I could see when both hands were busy holding the two ends of the screwdriver. I wished I would have had one of these head light attachment headbands(and I do now for next time)
Headlamp with Swivel Lens
I also got my switch from the same seller in the link earlier in the thread and it worked great.
Don't be afraid of this job like I was, it is not that hard. And get 2 switches and keep on in the car; my last switch was replaced just over a year and less than 10,000 miles ago.
Steve