I have a booster pump that has a seal leak, and it's getting bad enough to have to fix.

I'm comfortable doing light mechanic work. How difficult is it to replace the seal?

Also, based on a PB4 diagram at http://www.poolcenter.com/parts_pump...oster_pump.htm, is it recommended that I replace parts P-55, P-95, P-40, or just P-95 and P-40?