Just done one of mine.
The most easyest way of doing it is to wizz the Allen bolt out of the bottom of the fork leg. Job done.
But you do need a good compressor as I have a home one but didn't have enough puff in to wizz it out!
Once that is out take the spring clip out under the dust seal & pop the seal out & push the new one in spring clip back in, dust seal , pour oil back in , wizz the Allen bolt back in & your done.
(thanks to Dale Williams for back up info)
(ps , I forgot to take pictures till it was too late! )