An easy job for an experienced Minor tinkerer but can catch out the inexperienced. For instance don't forget to drain the oil out of the diffs before you start. It can make an awful mess.
First thing get yourself a decent workshop manual and read the relevent chapters thoroughly before you begin and support the axle securely on axle stands--SAFETY FIRST.
just to add to Mike's post, the other thing that can be tricky is replacing the half shafts, as the axle tube does not guide them accurately into the differential. You need to aim them to enter the splines. It can sometimes seem as though they will not go in. You also need to rotate them slightly so as the splines line up.
Good luck.
A straightforward job Steve. As the others have said, read through the job in the manual a few times and above all make sure the car is well supported on substantial axle stands under the axle. You will need some new gaskets, one for where the diff bolts into the axle and one for each of the halfshafts.