I used to own a 1988 780. It was missing the front air dam, the driver's side door panel liked to fall off, the seats were garbage, the V6 needed a lot of work, the right front fender was mended by a color blind Walter Mitty, the seat electrics mostly worked, and parts were non-existant.
It is not worth whatever the seller is asking for. $650 for a new air dam, door panels no longer exist, new leather seat covers are $1,000 each, and the engine will require an arm and a leg and still never run right.
If you have to have a 780, get a turbo model for $2,000 that already has an air dam and good seats.

Klaus