If there are only 2 leads, then one has to be power and the other has to be ground. If you reverse them, the motor will just spin backwards. You should only have to put power to it for a few seconds to prove to the guy that it works, so even if it's backwards you shouldn't do any damage. If you're really concerned, pull up a wiring diagram and find out which color wire is the power lead and then there should be no question.

95 Montero SR
3.8 MIVEC, Advance headers, 2 1/2" exhaust, Magnaflow muffler, OME shocks & rear springs, 2" body lift, 3" tank lift, 4.90s, TRE front locker, factory rear locker, Roger Brown Rock Sliderz, 315/75r16 (35") tires, Sport big brakes