Here'* my two cents to add to this topic, just to help anybody else doing this.
I pulled the old mirror off, pulled the passenger side A-pillar cover off, pulled the front 4" of the headliner down (if you do this, be VERY careful to not break the foam in the headliner and it will be much cleaner and easier to re-glue to the roof), and clipped the new mirror on.
Disconnected the wire harness on the mirror, cut off the plug and soldered two wires on to the ends (the pinout above is correct -- closest to the post is 12V, the middle wire is Ground). Plugged harness back into mirror. Ran the wires over to the passenger A-pillar, and spliced into the existing power/ground wires for my moonroof. Tucked all the wiring up into the headliner (if you push the wires back about 1", they will fit nicely where the curve in the headliner from the windshield is), put the wire covers over the wires between the mirror and the roof, and everything worked perfectly.
'94 Bonneville SLE | 266K miles
CAI - K&N cone filter - polished intake runners - 140 amp alternator - 2.5" exhaust - Magnaflow hi-flow cat - Magnaflow dual outlet muffler - 106K on engine and transmission - Sold 1/14/07
94 VW Jetta - 151K - 2.0 - 5 speed - Ghetto black steelie wheel mod - Techtonics 2.25" cat-back system