Read the thread stickied on the top of this page about I wanna watch movies! There is an over ride code in there to allow playing a DVD while in motion, I think they figured out Nav as well, but since I don't have factory Nav I've never bothered to read the whole thing.
Far as your question on the aux input connections I'll let one of the guys with more experience on that side of things answer it, I know there are some custom harnesses out there, but not sure what it requires to use one, cadillacSTS2003 would know the answer to your question.
if the cd changer is unplugged or the disks haven't loaded the cd button will go "hollow" but it's still there on the screen
when in nav map mode, the top right corner of the screen shows whatever audio source is in use in the form of a soft key, and when the navigation "chimes in" to give me a directional instruction a hollow key with "nav" appears in it's place.
I can't seem to find a way to get the aux to show up...
Couple of entries on the net about those being tv inputs but need other pieces. And quite a few saying play and play for audio... seems to depend on year alot and some don't mention their years unfortunately.
I could suggest they might only be video driven and possibly not show up unless device is connected?
The only other thing I can think of is maybe they're not hooked up to HU? never know...