You may not nave to remove the shaft if you can slide the fitting aft
enough to get good access to the surfaces and rotate the fitting enough
to clean it properly.

Yeah, but if the previous owner gunked it up with goo, and this guy added
more, then it'll probably require a bit more than just 'cleaning it off'.

Then there's the question of the hull condition around that whole box. If
it's been leaking then it's likely that water has gotten into the layers of
fiberglass. It may require a fair bit of fiberglass work to remove the
damaged portions.

This also leads to dealing with making sure the prop shaft is properly
aligned. The tolerances are pretty important.

It may be best to get a fiberglass place to take a look at it and give a
quote for proper repairs.