Just because the '93 has an M104 engine does not mean that the head gasket will fail for sure. It might fail tomorrow or it might go forever.

If the evap was replaced, it is likely that a copper one was used, but there's no way that I know of to confirm this. Is there a replacement part number in the service history?

The later 124 cars are definitely nicer than the earlier cars IMHO. The head gasket problem is a down side, agreed, but there's never any guarantee about any used car. Things could just as easily happen to a 103 engine.

Don't dwell too much on history. Pay more attention to CURRENT condition of the vehicle.

Best of luck,