I have an Aqua-Flo Flo-Master XP pump (model # 0662500-1; date unknown) that's leaking around the shaft. I assume a new seal is a good place to start to fix the leak. Is the PST200 (Ref. ID 576-0) sold on this sight the right replacement seal?

I can't say for that question, but I have a question regarding your shaft. Is it visibly rusty with possibly flaking or chunky rust? If so, you might want to order a new impeller as well.

I have not opened the pump or motor yet--I'll start that tonight. I did see quite a bit of rust on the shaft where it is exposed between the motor and pump. I'll have to see if I can tear in all down enought to assess and/or repair. May need a whole new unit. Thanks for the suggestion on the impeller--I hope that's as bad as it gets.

inside the pump won't matter, the shaft is only visible behind the pump, as you have seen. Here is some diagrams of what I found is an easy way to remove the impeller, in most cases. Normally the impellers are on so tight (thanks to the rust) that you will either cut your hands or destroy the impeller trying to get it off. Forgive the crudity of the pics, I'm not an artist.

Remove the endplate from the wet end (pump), and remove the rear cover (in some cases) or plug from the motor, to access the back side of the motor's shaft. Stuff a rag into the pump as shown, and using a screwdriver, plier, or what ever the case may requre, into the rear of the motor's shaft and turn. The turning pressure will force the rag into the pump/impeller and effectivly lock it into place, so all your effort is on the rear shaft, not in trying to hold the impeller steady.