Lift the 300ZX using the jack and place jack stands underneath the sides of the car behind the wheels. Then pop the hood and unbolt the connections on the battery, starting with the negative terminal and ending with the positive terminal, using an open-end wrench.

Crawl underneath the car and locate the alternator at the base of the engine, on the passenger side. Loosen the mounting bolts to the alternator and push it toward the driver's side of the engine. Pull the belt off of the pulleys.

Remove the adjusting bolt on the alternator, then remove the lower mounting bolt while holding the alternator steady with another hand. Then lower the alternator down and away from the engine.