Those are all the normal signs of failure that I know of as well.
Yeah, I would definately try to diagnose it some more and narrow-down the exact problem before I started messing with that circulation pump. They're not too hard to change (not as easy as a Chevy :P), but I would do that last after I had checked everything else.

I'm sure it's possible to rebuild-it, but I have never done one. Might be more work than it's worth to save a few $.