There are already a couple of DIYs that go through the whole process of retrofitting one of the fancy mirrors to our cars, but all of them seem to be for coupes. The convertibles are a little different, because the overhead console is different. There is a 14-pin connector instead of a 20-pin! It's the beige one on the left side that the retrofit harness goes into. The mirror connector is the same. Otherwise, the process is identical.
Here are the wiring diagrams - hopefully will save someone the hours of headscratching, Googling, and forum searching it took me tonight! This is from a v2 of the BMW retrofit instructions that has a couple of extra pages for the e88/e93.
e88-e93 wiring diagram 1 for homelink mirror by
kevinr1916, on Flickr
e88-e93 wiring diagram by
kevinr1916, on Flickr