/6 manifold gasket

The guy at Advance you spoke to is smoking dope.

Advance Auto lists the Fel-Pro Intake/Exhaust manifold gasket set # MS9610B1 for $11.88 and it's a store stock item. This includes the manifold to head gasket, the gasket between the intake and exhaust, the gasket between the pipe and the manifold. Even a complete \6 engine overhaul gasket set is only $58.00.

Advance Auto, Autozone and NAPA all have online parts catalogs, Advance and NAPA sites have pictures too. You really should look the stuff up yourself and just go to the store and tell them wht part numbers you want.