I did try to demo it, but I didn't understand the properties of playlists properly, so it wouldn't play anything :/

It's a Grand Prix, so i'm thinking more that it was a bad job wiring that triggered an anti-theft something or other in thr computer (how technical of me :P )

The guy running the store is paying for diagnosis at a local dealership, so hopefully we'll find out from there where this is to proceed...

Eh. Could be worse, I imagine!