You might want to confirm that it is actually the axle seal and not the knuckle seal. The knuckle seal (M136687 on my 4410) seals the rotating-about-kingpin axis knuckle housing to the MFWD axle housing. These tend to leak and if they leak on the outboard side the fluid will run down the inside of the tire. This may give the appearance of an axle seal leak which obviously seals the axle.
My tractor leaked here when I bought it (used '03 4410 in '07) and I had replacement seals on hand that came with the tractor. The repair procedure (dealer let me read tech manual) was straightforward. It basically involved removing front axle/hub assembly (easy via large bolted flange on housing), the tie rod and then removing a series of snap rings, clips, shims, bearings and washers to disassemble the knuckle. None of it looked really difficult and armed with a parts drawing one could reassemble w/o issue.
If you really only need the axle seal, that's real easy and would only require removal of front axle at the hub flange and disassembly to that seal includes a couple bearings, a spacer and a snap ring.
The beauty of it was I didn't have to replace my knuckle seals. I simply removed the front wheels, cleaned all of the grass, mud, etc from this area and viola, no more leak (6 months ago). When I checked the service history on my tractor, I found that these had been replaced before under warranty and probably for the same reason - crap jammed into the knuckle seal area.
