It's actually not rocket science. The manufacturer may want to make you believe that it is, but it's really not. I took a Rock Shox Monarch apart (even the damper unit) and it worked pretty well. Mine was way overdamped so i switched out the oil for a lighter weight oil. Pressurizing the damper unit usually goes over a valve located at the end of the thinner diameter shaft (or on the piggyback reservoir, if it has one). Usually that valve can be inflated with a regular shock pump using a thin nozzle Rock Shox adapter like the one that the second generation SID forks used to have before they switched to schrader valves. (it's still a schrader valve core inside). Now as far as the nitrogen goes, it's really not that important, the back pressure on the damper oil is (keeps it from foaming up). I never got to experiment with the shim stacks (that's the holy grail of suspension tuning) but if you have the instructions (step by step) and are willing to spend a couple of hours messing around with oil and such you could do it yourself. I also took apart a Noleen NR2 damper to replace all the seals and bushings. Simpler to work with but the pressurizing part via needle ball pump valve was a royal pain in the ass. In my case I wasn't really worried about breaking the parts since I got them really cheap...
