That's some good info. I'm going to copy it to this site in case that link/site goes bad in the future.
"MOST OF THESE INSTRUCTIONS WILL WORK FOR A LOT OF NEWER FORDS, BUT THE VEHICLE FOR THE EXAMPLE IS A 2004 FORD EXPEDITION! USE ALL INFO AT YOUR OWN RISK I WILL NOT BE RESPONSIBLE FOR ANY ERRORS OR DAMAGES!
The truck in question was a 2004 Ford Expedition w/ factory 6 disc in dash, factory overhead tv, and factory subwoofer in the rear. Once you remove the factory radio, the tv and sub no longer function. Here's the tips on how to change out the factory radio and retain the rest. In this case we were adding a unit with navigation. First off at the back of the radio are the 24 pin main radio connector, a 16 or 20ish pin connector for the tv, and an 8 pin connector for the subwoofer. All connections are done at the back of the radio. "