I have the same vehicle and did install a Pioneer F90BT with nav, camera, and Bluetooth. Nobody makes harness kits or a faceplate adapter and the rear sub along with the overhead DVD are on a separate proprietary bus. I decided to do without those and spent plenty of time with my nose in the factory wiring diagram to get the steering wheel controls working.
I know I'm answering this question 3 years later, but for others looking to do the upgrade, I do not reccomend it. This applies mostly to the 2003 Expedition/Navigator with factory Nav.