In case you haven't seen it, check out this DIY.

http://www.peachparts.com/Wikka/W123RearAxles

There is no "diff cover gasket", you use RTV to create a seal.

You do however need a new axle output seal.

http://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2014.cgi?command=DWsearch&description=003-997-83-47&I1.x=0&I1.y=0

A few hours on average can be expected.

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