1962 Surburban rear end lube and gasket

[Bigfeetny]

Hi all,
I need to change the rear end oil and gasket. The rear end is a mess with built up leaking fluid. I think it is the original rear end. My question is what weight fluid do I use and where do I find a new gasket? Just trying to get ready for next spring. I am planning on a trip to the Syracuse car show, but want to make sure the suburban is ready. thanks Al