Can NAV System be modified to play a DVD?

I just purchase a 2007 H3. Since the NAV system is run off a DVD, can I not modify it in some way to play regular DVD's?

It should play a DVD but not while the car is in drive. (I think)

You can use the NAV as a monitor, but you need an adapter and an external DVD Player!!

http://www.gnetcanada.com/navvideo-models-gnet_rgb_gm5.asp

http://cgi.ebay.com/Hummer-H2-Video-Converter-for-nav-WATCH-DVD-MOVIES_W0QQitemZ320031976818QQihZ011QQcategoryZ48605QQcmdZViewItem

PAC stuff is ALWAYS GOOD:

http://www.pac-audio.com/products/productsCatagory.asp?mmSearch=Factory%20Navigation/Video%20Integration