Hey, I'm in a similar boat. I have 2008 SE and an aftermarket DVD player. I'm planning on using the nav bezel to hold a monitor of some sort and may do a computer too.
My DVD player is mounted in the center console and is connect to a Clarion VA700 which provides 7 output connections. I've read for a Nav unit, you need a TV2NAV type device which provides a way to add TV/DVD to a Nav screen.
I am active on several Titan forums and there's a wealth of information there if you aren't familar with them. I also have copies of the service manuals which includes wiring schematics for the head unit.