Um, yeah... you'd think even for a for-profit flip someone would have at least addressed corroded screws and scratchy pots.
Glad that bass ended up with someone who will appreciate it. Rotate those pots fully about 25 times each, and see if that doesn't clear them up. Repeat this a couple times if need be. They are sealed, so
do not spray them with anything. A little patience and some lube will get those screws loose. (I like Break-Free) Sounds like you have some experience with these things so shouldn't be much challenge. If you need any parts though, the Alembic HQ is fantastic.
Congratulations & Compliments, and Welcome.

*incidentally, being a 1993, that is a first-year Epic. I think a pretty early example of the line too.