What seals does it have? The XXX or whatever they are? You simply pop them up with a screw driver, then pop the new ones in, you need to do this with the lower legs pulled off (obviously). They may have a wiperr seal, or fome ring just under the seal, thats pretty easy to get out too.
I haven't worked on Sid's before, only Psylo's Dukes, and Old, Old Judy's, but I'm pretty sure thats all there is too it. Check out AngryAsian for further help, he can answer almost anything...