dvd, 05 gmc crew cab

i have an 05 gmc crew cab with factory bose and roof mounted dvd player.i have a dvd player from an 03 denalli that i would like to add.i have taken the unit apart and would like to put the "head unit" in the lower cubby hole in the front of the factory console and the screen on the roof under the front roof mounted dome light/ cubby hole.i would ike to have them run independent of each other but i doubt they would ever be run at the same time.i sit in the truck ALOT waiting for the wife to shop and hate having to get in the back to watch a movie.

can i just "y" the factory harness out to the denalli unit?would it be possible for the front monitor to also act as an auxillary moniter?

any help would be awesome!thanks.