Well, if you drain oil into clean container, I don't see why you can't put it back in.
As for rebuilding, not sure where you'd get shaft seal. Which is part that wears out. And bearing. You can follow along with what's done here:
https://www.zl-oa.com/community/thre...e.21392/page-3
Coolant plays big part in water-pump longevity. Say no to Dexcool. Only use phosphate-free and silicate-free coolants.