That's right, folks. I took the leap and installed an AVH-P8400BH into my '06 Passat. Didn't hurt as much as I expected . I did learn a couple things though that should have been common sense, but I feel they could probably help other noobs out there:
1. The remote start wire on the harness adapter and the remote start wire on the HU aren't supposed to be connected to each other. This kept me scratching my head for a few minutes before I had to turn around and smack my face into a wall.
2. When you disconnect the battery on a '06 Passat, funny things happen the first time you start you car. I received a Steering Lock warning and couldn't turn on/off ESP (Stability Control). Instead of RTFM and see that this would alleviate itself if I drove forward a few feet, I started aimlessly pulling relays in the fuse box. This caused my TCU to poop itself and I had to re-pull the negative battery lead to clear the fault. So RTFM. It's that important.
So thanks all you CA guys out there. You helped me start upgrading. I look forward to being able to post more.