OK, it's not a difficult job, but it is potentially hazardous and takes a few people. If you don't have someone with you who's worked with these things before, then you probably need to put out a call for help on the forums or to the local MVT or IMPS groups. 432's are popular so you should be close to somebody.
If I remember correctly the correct sequence of events is
•Make sure the vehicle is on flat ground. Chock the wheels on the other side and make sure the vehcile is not going anywhere when you release the track.
•Split the track so it's not resting on the idler anymore (its very very heavy and has a lot of energy when it moves, be very very careful)
•Undo the big bolt on the hub (it looks like the odd one out) and drain the oil out.
•Remove the hub cover (small bolts toward the centre of the hub)
•Remove the inner cover (If I remember correctly theres a sealing cover inside that screws out)
•Remove the big nut under this cover (there's a locking washer the you can bend out of the way with a screwdriver and hammer)
•The hub can now come off the peg (be careful - it's very heavy)
•You can now swap the wheels over to the new hub.
The innards are very prone to damage due to mud and dust ingress at the back of the hub (there's no seal), so check for condition on the new one before you reassemble.
I can't stress enough how important it is to have some experienced help and to know what you are doing when working with track. It also needs special tools to split and re-join, so make sure you have them and know how to use them.
Where in the world are you?