In theory, you can re-build them yourself. You just need the proper tools, a large tank of nitrogen, a $250 needle valve assembly to put the nitrogen into the shock, and the parts to re-build it. Or, you can send it to a professional shock re-builder for about 30-40$ and let him do it. If you just need a re-charge on the nitrogen, larger dealers shoud be able to do it. You cant really just add a little oil to them.