Well, looks like we got a good deal then on our used one, assuming it isn't a complete lemon. Let's get the parts we need and run the tests. I'll cover the cost of the additional parts as well.
Depending on how the tests go with the unit on order, it might make sense to repeat the tests using a new pump. Of course, that would require a significantly larger financial commitment, something I'm not ready to commit to at the present. But, one step at a time. Let's see where things lead.