Removing the Nissan plastics
Gently pry the rain sensor cover off the screen. There are a couple of velvro-like clips that hold it on so don't worry about any scary noises when this is removed!
Pry the interior lights open like so (there are 4 clips holding each one on):
Unclip the centre section that holds the ambient light (your power supply for the mirror) and sensor:
The cables are quite short but the 2 devices unclip easily:
The Blue (+12v) and Yellow (GND) cables going to the ambient light are your power supply for the auto dimming mirror. The ambient light is only powered when the side lights are on. Do not power the mirror from the interior lights as these are permanently live and the mirror will drain your battery.