I just finished changing the shock oil in my step-sons WR 400. The bike has few hours on it despite it being almost 5 years old. The job was quite easy. I bought a Race Tech video from EBAY. The video was very good. It did not overtly promote Race Tech's products. Sure, it made mention of them, but it also showed a person how to deal with the stock parts. The cost of the shock oil was 14.95. I believe one bottle would fill the shock twice. We inspected the shock and the parts inside appeared to be ok. The oil was filthy. It stunk like rotten eggs and looked like chocolate milk. The only struggle with the project was finding a way to measure the psi of the nitrogen. There are guages available, but they are quite expensive. I carry nitrogen on my service truck but there was no accurate way to measure the shock psi. The volume is so low that using a standard guage would release 30-40 psi of nitrogen. This was no good. I decided to spend a few dollars at my local "Race Tech" certified facility. We agreed on the price, 5.00 and went to the back room. The tech then adjusts his 0-3000 pound regulator to @ 175 psi (regulator was marked in 50 lb sections) and held it on my shock "until it sounded full". I grabbed my shock and left. I ended up filling with my own manifold guages. I know I am much closer than his "sound" method. Overall, this was a positive experience. I was left with an appreciation for the Race Tech video, but I was extrememly dissappointed in the way race Tech monitors their dealers. I am sure there are good ones, but I certainly found a bad one. A massage therapist must have a license to offer people "manual release" but apparently Race tech will certify anyone smart enough to stick on a decal. It makes no sence to me. The instructions here http://www.mx-tech.com/downloads.asp were also very helpful. On a 1-10 scale I woudl rank this job a 7 in difficulty. Slightly harder than fork seals and bushings. teh worst part was bleading the shock. It is messy.