HELP !! Water pump replacement advice...

[SoCal LS-L]

Hey guys, went out to the ol war wagon today and discovered shes been bleeding coolant bad all night long. She only does this when cold.... after getting warmed up the leak stops. It is definitely coming from where the water pump mates to the engine, so I need to do the gasket. I cant afford a timing belt kit right now or even a new water pump, so im tearing it all down just for the gasket (time is not an issue, money is). My question is, what other gaskets might I have to replace when removing and resealing the water pump?? Its my only car so I want to be ready from start to finish and not have to stop and walk to an auto parts store to wait 7 days for a new part. Any pointers would be appreciated.

P.S. I have a black metal filter (looks almost like a fuel filter) adjacent to the water pump that seems to be connected in/out to two lines coming from the bottom of the radiator. Is this an external transmission filter??