Tower Jack,
This link will take you to the PIE adapter. As far as I know, they're (PIE - Precision Integrated Electronics) the only ones who make an adapter that plugs directly into the back of the Ford factory radio. It plugs into the jack that's used for the rear seat entertainment system and allows you to use the AUX button as the auxilliary audio input. The adapter is $89.95 and here's the link to get to it: http://www.logjamelectronics.com/log...efrd04aux.html

Installation was a breeze after getting the bezel off. The adapter also has a line level adjustment on it. Works great!
Hope this helps...
Take care.