Had a mirror for sale forever, well decided to tackle on my MINI.
From the factory, my MINI had the Homelink/Auto dim mirror. I installed the other mirror, new from MINI w/compass, but couldn't get the key programmed. I thought about rewiring, but all I really did was take both mirrors apart and installed the radio module into the mirror with the compass. The compass wiring is on the self dimming wiring. Everything works fine, even though two wires on the radio harness do not line up. Lock/unlock/trunk all work fine. Compass had to be re-calibrated.
Now, my only regret is not taking pictures, and the ring that holds the ball joint in the arm, I could not get back on-still snapped together.
What I REALLY don't understand, is how all these parts are not available separately;harnesses, homelink module, radio/remote module, the mirror casing, the two metal frames inside, the actual self dimming mirror part.
So, with the "parts" that I have, I may wire into the self dimming mirror part into wife's MINI...who knows.
I can take pictures of my "old" mirror if anyone wants to see.