I just put one, with compass in my car. Make sure you get at least 16-18" of the wiring harness, or you will have to extend the wires.
You only need a ground and 12v+ to make the mirror work.
There is usually another wire to cut off the auto-dimming feature in reverse. If you want, you can run a wire that taps into the wiring for the reverse lights to have this feature as well. If/when I take the interior out of my car, I may do this.
First, make sure you can remove your rear view mirror without popping the button off of the windshield. I couldn't, so in my pic, I'm holding the mirror up.
To be noted - the mirror button in my 92 was different than the one for the auto dimming mirror - I do not know if later gen 2's switch to a different button style or not.
The mirror button for the auto-dimming mirror is on the left, the one the car had is on the right:
If you have a sunroof, your mirror install will be easy, you just need a ring terminal, and a wire tap.
Crusty old mirror:
I removed the sunroof switch assembly from the headliner, and also the removed the two clips for the sunvisors, to allow me to pull the headliner down enough to fish the wires through.
Wiring info is here
http://www.the12volt.com/installbay/forum_posts.asp?TID=8560&KW=177
The mirror I had was from a Ford, so the colors were different - for ME black was the ground (obviously) and purple with a red/orange stripe was 12v+. If you are unsure, just use a drill battery to power up the mirror to find which wire requires the 12v.
For the ground, I just put a ring terminal on the end of the wire, and removed one of the screws holding in the sunroof motor, and, put the ring terminal there.
And for 12v power, I checked the wires that go to the sunroof switch to see which one had 12v when the ignition was on. That was the blue w/black striped wire, so I tapped into that.
Plug it in, turn the key to on, and, mirror: