Advice on changing the key in the keyway of the crank in a 1991 300z?

To change the key in the keyway of the crankshaft in a 1991 Nissan 300ZX, first ensure the engine is completely cool and disconnect the battery. Remove the crankshaft pulley by unscrewing the bolt and using a puller if necessary. Once exposed, gently tap the old key out and replace it with a new one, ensuring it fits snugly in the keyway. Reassemble the pulley, torque the bolt to the specified settings, and reconnect the battery.