Run the wires up the A pillar and along the headliner to the factory wiring.
Slide the new mirror into place. Be sure you put the plastic that holds the plug back on it.
Plug back in the factory plug, and attach the two wires with tape, or your method of choosing. I since changed the install slightly.
There isn't a lot of room here so I ran each wire along each side of the factory plug and tried my best to snap in the trim.
- Old method
After not liking the my mirror was "taped" I decided to see if I could find a method that I could retain using the pins on the mirror. If you have old junk PC parts laying around, I did it using an old CD Rom audio cable hookup.
I soldered in and taped up the CD rom audio cable to the two wires that run up the head liner.
I used two of the 4 holes one on each end.
I pulled the other part of the audio cable off of an old motherboard, shoved that into the connector, and taped up the remaining part of the cables.
Behind the factory connector is the CD audio connector, and I just plug the wires in now.
I verifed my onstar worked by using the virtual advisor, and when I drove at night the auto dimming worked fine as well.