Yes you can. I would put a new pump in if your going to put all that work in to replace the o-ring. You are going to be kicking yourself down the road if you don't. But if money is a issue I get it.
What up Mike! Welcome. You from the east side huh? Look for my truck at the tiki hut. Thats my spot. If you see it stop in and say hi. Everyone there knows my truck they will point me out.