Well, just the seals anyways. A few days ago, my pump stopped working properly. It would get maybe 10 strokes in and then the pump just would not come back up even when pulled with all my strength. Figured, since I don't have any warranty on this pump, there was nothing to lose by taking it apart and trying to figure out what was wrong with it.
I was able to make my pump work again by replacing the o-ring in the check valve and on the pump rod. I also wipe out the gunk/lubricant that is collected at the bottom of the pump. Very nasty indeed, and it seems some of it may have been pumped into the gun, definitely a good idea to keep it clean.
For reference here's the Hill pump diagram. The Discovery pump is similar to the Hill pump, but I'm uncertain if the seals are the same. Airguns of Arizona does sell a rebuild kit for the Hill pump.
The Discovery pump is very similar, except it only has 1 ball intake port and there is an o-ring behind the little white seal on the rod. There were a few other o-rings here and there that were a little different, but nothing major. Wish I had taken pictures when I had it apart. Probably will need a rebuild again, as I used cheap o-rings and no lubricants at all.
So, if you're warranty is out and that pump fails you, take that bastard apart and make it work like new again.