To service the assembly you remove it from the wheel and perform the following:
Take off the snap ring, flat washer and remove the tongued drive plate first, then using a small flat tipped screwdriver place it alongside the centre drive collar and slide it under the seals lip, then lay it on an angle to the edge of the outer housing.
Once you have the screwdriver oriented properly pry up onto the seal carefully, use enough force as its a bit of a tight fit in the housing but dont abuse it.
Once the seal is out you can lift out the drive collar and take out the other flat washer thats underneath it.
For removal of the drive shaft itself use a needle nose pliers and span the opposing slots in the face of the bakelite retaining collar inside the hole. Once its loosened keep turning it till its out, you can then extract the shaft and the two flat washers on each side of it.
Clean up all the parts in solvent and then refit them using a good quality grease, it should turn smoothly once all the parts are reinstalled.
If you want to go the whole hog and refreshing the housings finish, remove the old paint and or corrosion and prep it for some new paint. Rustoleum make an engine enamel thats highly resistant to solvents as well as heat to 500 degrees, this works quite good for aluminum even though the silver colour is a bit dark. The housing in the photo has had this same paint applied to its outer surfaces.
In the following picture the oil seal is NOT shown.
