is it possible to some how 'rig'/modify it to play dvd movies thru the existing dvd player and the navi screen?

sorry if this is extremely dumb question... i dont know much about stereo, electronics, etc...

 

has it been ever done?

you got the player.... you got the monitor.... hmmm.

 

no... No one has gotten the nav dvd to play dvd movies, and no one probably ever will. You have other options though. Buy another dvd player and use the existing monitor to display it via www.nav-tv.com or www.videonav.com or "AVelectronics"