Only real hard thing on the enfields for the unwary is not taking the top fore woods (hand guards) off then the bottom fore wood off before removing the butt stock on the MKIII as they have a recoil plate (not visible when assembled) at the back and when you turn the stock bolt its square head forces the ears of the plate apart which can split the back end of the bottom fore wood which is rather sad......

The hardest part of the lee's both the MkIII & No.4 is fitting of a new bottom fore wood but if your confident and good at wood work then you can do it as there are scads of threads here by the experts on how to do this anything to do with the action like replacing barrels or bolt heads I get my gunsmith to do it as its allot more involved than just chucking on a new bolt head to get it into spec.
I have pulled my Parker Hale bolt head down to clean it is based on the Mauser 98 action and they are a piece of cake to do I agree with Aragorn the K-31 bolt is complicated and the Lee enfield is the simplest.