Its not all that hard
Drain the chain case by removing the plug that is under the back, its covered with a plate with 3 screws. remove the wheels and block it up. Remove the covers on the chain case, there are 2. You can do this second part 2 ways, one with the machines power or remove the hydraulic motors to allow them to rotate, this is your choice. Use a 1 1/8" spanner on the bolts inside the chain case, use the drive to crack the bolts or make a jig with a length of pipe to slide over the wheel nuts.
Once the bolts are all cracked you will need 2 good sized hydraulic jacks to get the hubs off for starters. Loosen the bolts on the hubs, put 2 bottle jacks behind the hub, one each side with the pump facing down wards, pump them up then either strike the head of the bolt with a copper hammer or the back of the hub, it should pop free. Don't fully remove the hubs yet.
You can use the hydraulics to spin the bolts all the way free or by hand. Either way, remove the bolts. You then use a bottle jack behind the hubs and push the axle and seals/bearings out. The sprockets will slip off the axles. Now use a length of bar and knock the bearing cups out, you can get them all if you have both rear or front axles out. To re-install you can machine a tool to pull them in with a length of threaded rod, tighten it up to pull them into place, simple job with a lathe. I used a piece of water pipe to seat the bearings on the axles, i used a welder and air chisel to get the bearings off.
Slide the axle in, grease the bearings!!! line the sprocket up on the axle and slide it all together. Put loctite on the bolt and tighten up! Check for end float, there should be no play with new bearings.
Do the same for all 4
You may need to make a seal installation tool too, i made one that i slide on the axle and slip a bolt through and tighten up to pull it in, no bashing required, very simple to make with a lathe.
I hope that gives you an idea whats involved. If you have a lathe and time, you can do it easily.