Installed a unit for a buddy with the 2nd gen sync with Auto AC today. Pretty much the same install as 3rd gen sync, except the sync brain attaches via a cpu like connection squarely in the middle of the brain. I wasn't sure which side was "up" so we guessed at keeping the writing facing up and it worked. There also wasn't a connection for the extra speaker to plug into. There was a wire labelled "speaker" but it was plugged into something. So we ended up not plugging in the speaker since it didn't really work on mine anyway.
I'm not sure where the 2nd gen sync GPS plug is, so we used the included GPS puck. No option to use the factory GPS antenna like I did with my 3rd gen (without nav, all I lose is the compass). Other than that the install went great and the unit is working fine. I'm 2/2 on working units so far...