dont quote me but as far as im aware just look for the same issues you would with any other forks.
Hard to explain really but if they make a 'thump'/'clang' sorta noise when you fully compress them they prob will need the needle bearings resetting.
I havent attempted it myself but if you do a google the whole process seems pretty straight forward with nothing much to go wrong if you follow the instructions.
With regards to a full service(new oil, seals etc) again there is some step by steps if you google. I think some models do require a special tool but if i remember correctly the HT2 BB tool does the job.