This is the second mirror I have had. I opened the first after I could not figure out the wiring. Even jumping the wires to eliminate the curcuit board is a PITA plus the mirror was sealed pretty good. After screwing it all up I just got another mirror to try again.
Anyway, I inserted the two diodes and it all works like a charm. I have domes off the dome switch and map lights triggered by the mirror switch and powered by the ignition so I don't drain the battery. It works according to my diagram and I am pretty happy although it too way to much work to figure it all out.
The mirror is a Donnelly 10110109 mirror and I used two of the 1N5400 diodes from Radio Shack.
I did a quick write-up on the whole thing here...
http://www.cb4x4.com/forums/showpost.php?p=40165&postcount=1