I am pretty sure that is would be pre-wired. But if you get the oem you also have to send in your navigation unit to get it reprogrammed to recognize the dvd player.

Another option is headrest monitors. You can buy replacement monitors and have two separate dvd players. They are under $1000 on ebay. Here is one set.

eBay Motors: NEW OEM FORD EXPEDITION HEADREST DVD VIDEO PLAYER (item 260317725430 end time Dec-17-08 17:16:26 PST)