Hey buddy, welcome to the Mac Car realm!
I cannot see the picture for some reason, but I googled that particular vehicle, and can only imagine the antique you have there!!
As far as the screen defaulting to a camera view, it is possible. On my Lilliput eby-701, there are several connectors; one I have reserved for my rear camera, and the other in use with my mac mini. No plug-in intended, their newer models are supposedly pre-wired so that when you shift in reverse, the monitor automatically switches to rear-view mode...
Something to think about.
In any event, please repost the pic of your Metro Van, and best of luck!