Thank you ftillier - You're bang on the money with the instructions (it's super simple as well), here are some notes/images for those that follow, first put the mirror to this position (pointing inboard):
Gently pull it in the direction of the vehicle (horizontally) by putting your fingers on the outer exposed edge.
I had trouble disconnecting one of the following two files (on both sides), I used a screwdriver to pry it off, here's the inside of the mirror assembly:
Here's the resistance of the left mirror (driver - flat mirror - 397ohms):
Here's the resistance of the right mirror (passenger - convex mirror - 1018ohms):
The two differences alone tells me there's an issue! Here are the codes I have:
DDM (Driver's Door Module), left mirror heather output code is B1163-15
PDM (Passenger's Door Module), right mirror heather output code is B1164-15
Given it's cold here in MI I suspect these should be "on" and could look for voltage, I'll try to do that another time!