Bob,
I am thinking that a pair of circlip pliers might be the tool you are talking about (If Tman sees your thread, he will know).
Sorry to hear about the leak. After repairing my old Coleman tub an number of times (and wasting my money once on that crappy stop leak product, as well), I decided to get a new tub. I gave my old tub to a retired friend that needed a project, so I was very happy with the Coleman going to a good home.
Good luck with fixing the leak. Sometimes they are not too hard to locate. Other times they are a major pita. I'm sure the full foam guys will be hammering me in a few minutes over that comment.
.