Happy to help. I was all ready to do it when my mirror arrived this week only up show that it's completely different from everything else posted here. In fact, I created this account just to post the wiring to help others.
Not sure if you figured it out but thought I'd share since I just got this same mirror.
This is how I wired everything and it is working great:
Black wire in the mirror harness is Ground. Splice it to black wire in the overhead light harness.
Green wire in the mirror harness is your constant...