4WD is a bit complicated and I've not done it.
2 or RWD as it should be known - remove wheel, hub cover, split pin and castlelated nut, undo and slide off the brake calipher(hang it out of the way mind the flexi hose), carefully pull the hub and disc off be careful of the bearings dropping out and dirt.
Replace disc and pack hub with grease refit and job done.
Hub nut done up until the hub binds slack off until you have acces to put the split pin in and double check.
HTH