Just tap into the sunroof power wire, you can catch it on the sunroof control module and it is the yellow wire in the small connector.
If you want reverse undim function for when you back up you can catch the backup lamp wire by removing the back seat and rear deck carpet and its the light green wire in the harness you will see goint inside the trunk, Test with an ohm meter to make sure it is the correct one as there may be some for the sound system, etc
To go from the mirror to the back of the car just run the wire along the roof harness which is behind the headliner on the passenger side.
