The TV-out is connected to my car's navigation system auxiliary A/V

Yours has that? Isn't that illegal somehow....

any idea how I might do that?

Seriously, I was looking around the DVD box that runs the mapping software for my NAV system for some sort of A/V connection, but they've got that sucker bolted down nice, and I don't feel like taking the seat off. I don't think it would work anyway...oh well. I just would love to be able to be waiting in my car for someone, and be able to switch over my lovely NAV display and watch a DVD or something.