If there are no rips or hole's in the gasket you should be fine in
reusing it , cleaning it warm water little dish soap then dry it
as far as the rust could be worse than what you think
or it may not be that bad at all , I would take a wire wheel
on a drill and clean the rust & failed paint away first.
(Make sure the Gasket & door liner are off So you don't damage them)
Pat
