Yes you generally have to:
- http://www.4crawler.com/4x4/CheapTricks/AxleRebuild.shtml

There is a shortcut method to getting the whole knuckle off, but if the seal is leaking gear oil into the birf and possibly the hub, you probably want to clean that out and inspect and regrease everything at this time. I had 2 leaking axle seals for about 3-4 months and ended up having to replace 2 of the 4 wheel bearings and 2 of the 4 knuckle bearings as a result. Oil washes the grease out then the bearings don't hold up very long.