I see a large o ring on the parts diagram inside the front wheel, but I don't see a seal kit for the wheel/axle assembly. Is this all that needs replaced if it is leaking axle fluid on the inside of the wheel?
There are a number of seals that can be at fault, but before you go ordering parts do a quick test. Raise the front wheels off the ground with the loader, and check for play in the upper/lower kingpins/balljoints. You shouldn't be able to wiggle the wheel and feel it move in the housing. Normally just grab near the bottom and try lifting...you'll feel it. When the kingpin/balljoint wear, they allow the shaft to move, and it beats up the seals. There should be a seal at the end of the axle housing, a seal on the inside of the swivel housing, a seal in between the inner and outer bearings where the swivel housing and inner planetary hub meet, and then the o-ring seal on the outer planetary housing. The most likely culprits are the seal at the end of the axle housing or the seal at the inside of the swivel housing. I just went through this on the left side of my Super M, and I'm literally in the middle of the same thing on the right side.
How big of a job is it to change these seals?
Not terrible, but not exactly a quick project. You have to remove the tire, drain the planetary and center pumpkin, remove the planetary cover, remove the gear carrier and gear ring, remove the upper kingpin and lower balljoint, disconnect the steering tie rod (two big hammers beating on the housing to pop it loose), pull the swivel housing off, then pull the axle shaft out. Of those tasks, the hardest part seems to be separating the lower balljoint. If there is any play in the balljoint or kingpin, you would want to replace them (aftermarket kits about $125 per side). The hard part there is getting the king pin bushing and balljoint race out of the axle housing. I've been able to get the balljoint race out with a harbor freight hammer type bearing puller, but the top bushing is much more difficult....heat it with a torch to cherry red, let it cool, and it usually pulls out with only finger pressure. Replacing the seal that goes between the swivel housing and inner planetary is a bigger job, and the two bearings and one seal will run about $200. The axle housing seal is pretty easy to get out with a puller, or even pry it out a bit at a time with a vice grip by rolling the lip back towards you. The same is true of the swivel housing seal. Replacing them is simply a matter of finding a socket that is a bit smaller, and taping them into place with a hammer.