I've done this mod and it's a very worthwhile upgrade.
Simply change the front 10" drums and backplates for the 11" items. The pipework should even re-connect easily as the upper cylinder connections are in the same place.
Put the old 10" wheel cylinders from the front onto the back to keep the brake balance correct as these have slightly larger piston bores. Again, it's just a nut and bolt job.
The early (small) master cylinder doesn't have the fluid capacity to move all six wheel cylinders satisfactorily so yes, you should also change to the later, larger unit.
The hardest bit of the conversion will be the bleeding but if you use one of the pressure blleding kits and work your way round the wheel starting with the one furthest from the mc then it should go OK.
Hope this helps.
