Check the oil pressure and compression readings before you decide what to do. Better yet, get a full inspection by a good mechanic. If the motor is in good shape, it may well be worth fixing the rest of the car. If the oil pressure is low, or the compression is poor, then part it out and make a nice profit.
Also, the tranny problem may not require replacement. It could be a sensor or something. So get the codes and post them here so we can go over them with you.
