From another website which I used to do mine. The gist I got from researching it that it is worth diy as the cost is in excess of the forks value, and parts are near impossible to get hold of;
1. Took off wheel and brake assembly, then removed handlebars, etc., and pulled out the forks
2. Unscrewed the allen key bolt on the gas damper side (RHS on my set) and the nut on the coil side
3. Undid the large nut on the upper end of the gas damper stanchion using a 27mm socket spanner
4. Undid the (admittedly flimsy) plastic 12-toothed nut thing on the top of the coil stanchion using a mole grip - this was the diciest part of the process and I'm not sure how many times I'll be able to do that before shearing off all the plastic teeth! (Presumably there exists a special tool for extracting these doo-dahs) By the way, all nuts and bolt undo the conventional way - there are no reverse threads, even though to begin with you might think so, as they can be VERY tough to shift at first!
5. Pulled the stanchions out of the large U-shaped piston-tube thing. They got stuck at first (due to all the muck and stuff that was lurking inside) but a few well-struck taps with a rubber mallet soon brought them out
6. I soaked the spring in a measuring cylinder filled with paraffin while scrubbing the chromed outers of the stanchions with a green plastic kitchen scourer and hot soapy water
7. I used a piece of wood (broom handle would do) with a green scourer stapled to the end to scrub out the big U-tube thing (since it was caked with all manner of crud)
8. I used a slightly more refined process with paraffin and old rags to clean out the inside of the chrome stanchions
9. I left all the bits on the top of our Rayburn to thoroughly dry out before applying Manitou Prep-M (the only fork grease my local bike shop sells) to the bottoms of the forks, the coil, and the chrome stanchions just below where the rubber seals go
10. Then I reassembled the whole lot. Seems to be working good as new. I'll update this post in a week or two once I have given them a good testing, although to be honest, they were compressing and then staying down, so they were no good at all before I took them apart to clean them up!
hope thats some help!