There is a way of changing it without pulling the hub apart. If you remove the spring from the new seal and un-thread it from itself to open it out, cut the rubber seal with a sharp knife and then cut the metal ring with a hack saw to complete the cut you can then open the ring and thread it round the axle tube (yes it will go, just. Best buy two replacements just incase though). Once over the axle thread the spring back into itself and locate it in it's original position, then install the lot into the swivel hub with the slit in the rubber at 12 o'clock. Put a smear of hylomar blue over the slit in the rubber for added peace of mind.
I did the drivers side on mine that way 4 years ago and the passenger side a year ago, both are fine.