Definately have talk with the manager/owner........................

Put the key in his hand and let him know that at no time is it to be out of his possession. If he cannot guarantee that, go elsewhere. You might also inform him of the value of the car and the value of the engine alone. A good trick to disable the car is to trade the dist end of the coil wire into a spark plug wire position and put the plug wire in the coil hole......I think as was stated prior that crossing 2 wires might blow a power valve, beyond that I don't think it would hurt anything. RonW