Sounds like it needs a DSG reset as a minimum. Otherwise a fluid change might be in order too, needs doing every 60k at worst.

DSGs don't cost 12k, there's very little chance that the rotating parts of the box are shot.

A mechatronics, if that was bad, is around 2k.

Personally if there's any doubt move on to the next one. If it's in a dealer's somewhere, have them get it looked at before you consider handing over cash. If they won't,walk away quickly.

Gavin