Done mine a month ago with 10w fork oil never made any difference except i know its fresh oil, going for 15w next time "probably in the next few months as the forks are shite" its a simple job just got to make sure you leave the same air gap in each fork, i made a simple tool with the correct airgap marked on think its 121mm off the top of my head.To take old seals out i just take circlip out then push a thin screwdriver through the old seal and yank it out then put new seal in with the help of a bit of plastic pipe,bobs your auntie job done.
Hardest part is screwing the top of the forks back on when you have refilled and pumped all the air out,the threads are very fine and you have to be careful you dont cross thread them also you are pushing against the spring which doesnt help matters,but if you take your time if you aint done it before you will be ok.