do you have the 4:3 or widescreen? If you have the 4:3 you can get a cheap 4:3 tv tuner and just hook it up.
You'll get everything except the navigation ( all menus) and your stereo won't shut off after 2 minutes. That will give you more time to search for a nav unit.
If you already have a tv tuner, just unplug the blue plug from the nav unit and plug it into the tv tuner.