Does anyone know where the procedure for changing the oil is on the 280Z, including how to reinstall the drain plug? It doesn't seem to be anywhere in the tune-up section. There is an entry to tighten the drain plug 14 - 22ft-lb. Is that all, besides using a new copper crush washer with each oil change?

Pretty much. The owners manual doesn't even mention the washer, but it's smart to replace it at least every couple of changes.

What do u mean reinstall the drain plug. Its reverse of removal.

Essentially, yes - but there is a copper crush washer between the pan and the drain plug. If this ends up too deformed, it can leak.

It's just a safe bet to replace it from time to time. Otherwise, yes, remove plug, drain oil, reinstall plug.

I've never replaced copper sealing washers, just anneal them with each oil change. Tighten the drain plug to German torque specs and you're all set. It's not very difficult.