I'm about to pull mine apart soon.
I bought a belt & both pulleys to replace at the same time.
I didn't get new hoses as these didn't leak.
Regarding the O-ring, I would take the one you have to ACE hardware and just get new ones the same size, probably made of Viton or Kalrez.
Great suggestion regarding taking the o ring to Ace.
![Thumbs up :thumbsup: 👍](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f44d.png)
Regarding the hoses, mine were kind of trashed, so I threw in hoses too. I just made sure to buy a pump with out a pulley so I could put to use the pulley and remover/installer tool I bought for the original job.
![Winking face with tongue :stuck_out_tongue_winking_eye: 😜](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f61c.png)