I wanted to share my story performing my map light rearview mirror retro as my experience was more troublesome than many and I would be interested in feedback from anyone that has perhaps run into the same problem I did.
I procured a good working unit from ebay and referenced the DIY article (among many others) at
http://e30.bmwdiy.info/lighted-mirror/index.htmlThe problem I had was when removing the old mirror from the metal base plate in the car, in that I found the backside of the mirror mount head seemed to have made contact with some sort of glaze (my car is diamond black metallic and the base plate is painted body color as all are) from the paint drying and caused the base plate to get stuck to the backside of the mirror mount head. After an hour of wiggling around every which way with no success, I decided I just wasnt pulling hard enough.
You have that instinctive feeling that hits you when you are pulling so hard you think "this must be too hard"...and it was :eek:
My old mirror came out WITH the base plate still attached, pulling the base plate from its rivet mouts that have holes in a piece of metal across the entire front of the roof that is stamped into the roof itself.
After much consideration on any way to address the issue with re mounting with any hardware solution, JB Weld became my friend for the first time (there was another solution but only rated to 200 degrees F and the black metal on the roof will get hoter than that on a 100 degree day in the sun.)
Anyhow, the wiring proved to be the EASY part in my case:)
No check panel here, so 12V was coming from down somewhere else!
I just spliced in off the glovebox flashlight charge circuit, this is on a similarly loaded 7.5A circuit as it would be wired from the factory or the check panel method, PLUS it's always hot so map lights work without a key

MY RECOMMENDATION on a solution to this is to:
Totally remove the headliner / sun visor trim (sun visors, sun roof hardware, a few screws) and use a LARGE standard screw driver (flat head) to run between the mounting base plate in the body and the mounting head of the mirror itself to ensure seperation. Many mirrors' spring loaded double nipple mechanism's are very tight due to age and barely will come out as it is.
Anyone else gone down this road?
PS. it's slightly bumpy :p