Hi mate
The kidney box is just a tight fit into the block with nothing holding it in so a bit of a twist and a pull should have it out.
As i said earlier there is a small pipe attached to it that goes into a pipe into the sump so just disconnect one end of that from either the sump or the kidney box itself.
The problem with working in that part of the engine is the manifold and the coolant pipes going to the modine on the oil filter but you should be able to do it without too many problems.When you refit the kidney box put it at a slight angle so the breather pipe can pass through the manifold without getting kinked.
If the pipe you have is slightly too tight to fit even with the kidney box out then put it the end in a bowl of boiling water for a minute or two before trying to push it over the spout on the kidney box.