^^ Thanks. I'll do the new chain first. I do think it's the primary problem.
I'll get the tool later. It is a good idea. The bike is 30 years old, after all, and it's been stored and transported with the back wheel off (and the RD not removed) several times in its life. In the meantime, I'll improvise a tool somehow, or have the LBS check it, yeah.
Thanks again!