THe turn signal/multifunction switches in these cars are a pretty common problem. It is a very good chance that this is your problem. The other issue is when he changed the motor, he may not have hooked up all the engine ground straps and the sound you hear is the car seeking it's own ground by backfeeding the circuit. Since the battery is going dead, I'd change the multifunction switch, as it sounds as if it's drawing power when the car is off. You can pull the negative cable and put a multimeter set to milliamperes. If you have a draw of more than 5mA (give or take a couple) with all electircal accessories off, you have a short to track down. You can start pulling fuses and relays (one at a time of course) until the draw drops. This will narrow down the circuit where the short exists.