Its no work at all the change your gasket while you're at it. A good rule of thumb is to ALWAYS replace a gasket when you are working on something that has a gasket. Why run the risk of a pinched old gasket or craked one or even an old one when you can spend a few more dollars to put a new one in. It NEVER made any sense to me why people would go about tearing apart an engine or any part of it to do work and not spend a few extra dollars to get a new gasket.
Would be that rubber one that goes between the valvecover and head and the small triangular metal gasket of the oil breather tube that connects to the valvecover (just above the alternator). I have reused mine a couple of times already without leaks.