In order to remove the dimmer switch you must take off the gauge console surround. Then you will see 2 bolts for it, one on each side. Just unscrew them and pull it out.
you need to remove the plastic cover under the steering colum to access the bottom bolts on the gauge surround. Also you need to pull out the headlight and defrost switchs and unplug them before you can remove it as well.
no, there are 4 altogether. 2 philips screws on top (you'll need a really short screwdriver to get at them) and there are two on the bottom. Once you have them out pick up on it first there are two small plastic prongs that pertrude from the gauge surround into the dashboard to hold it in place as well.
Forget the short screw driver for the two screws on the console facing the windshield. You're better off getting the torx bit that fits into a ratchet and get them out using the ratchet that way. A whole lot easier.
Changing your dimmer will be a pain in the a$$. You may consider if you want to install whiteface gauges while your at it as you'll only need 2 more steps to do that.
As I did my MAC whiteface guages last May, I'll give you a quick low-down on what you need to take off in order to get to the dimmer switch.
1. Unplug your battery. You'll be working with electrical stuff so you don't want a short. Also, you'll be working around the steering wheel so if you have an airbag, you don't want that going off too.
2. You'll have to take the steering column off. Usually held by 2 screws under the steering wheel.
3. You'll have to remove the light switches and defrost switches. This is made easier by doing this while the console is still bolted down. To remove the switches, look behind each switch and you'll see a plastic square clip. The hurdle here is to press down on each clip on each switch at the same time and gently pull the switches towards you popping them out of their housing. Careful with the clips. Old plastic breaks real easy!!!!!!!
4. Unscrew the 2 screws above the console below the windshield.
5. Remove the lower panel below the steering coloum. Held by 3-4 bolts.
6. Unbolt the two bolts holding down the console that are now exposed after having removed the panel.
7. Unscrew the lone screw holding the console down to the dash located between the 2 center heat vents and the steering column.
8. Double check there are no other screws holding down the console and gently lift the console up and away from the dash.
You should now see the 2 screws holding the dimmer in place. Unscrew, then unplug the back of the dimmer switch from it's harness.
Doing this job should take you about 2 hours if done slowly and properly with cleaning the parts as you reinstall back into the car.
Have fun and let me know if something doesn't make sense that I've written. My car is a 1990 5.0 by the way.