I just bought a 2011 Navigator with the THX w/nav system in it. It does not have rear DVD from the factory. It does play DVD's in the front as long as you are in park.

Question is, can you install head rest monitors in the rear and have them see the picture from the factory unit? I do not like the 4 foot long ceiling unit they have from factory with the tiny little 7" screen with controls at opposite ends only an orangutan could reach.

And, will they still be displayed while the vehicle is in drive...? Thanks for any input.

If you take it to a really good audio shop, they should be able to do it for you. They will have to find the wiring diagram and wire it in for you. anything is do-able though