I have decided that my fork does not work the way it should. It does not feel as plush as others I ride, and I don't see it working like I do others when they are just riding around the parking lot or grass.
Also it is not locking out, and the negative air pressure chamber does not hold pressure for more than 90 minutes(maybe less).
It is a Rock Shox Sid SL 2002 model or so.

I have looked at service manuals on SRAM website. How hard is this to do yourself? What should I watch out for, where would I buy new parts?

If I did not do it myself what would I expect to pay someone, and where would I go?

Thanks,
Eric