If you email Mike Roberts, I am sure he can give you the real world instructions to change it. I know its not difficult but access is the issue.
I believe there is no locking tool used, I believe it is done with a dial gauge down the spark plug bore to get the piston to top dead centre (TDC)
When your indie does it, tell them they MUST remove the water radiator as the quick method is to unbolt it and pull it to one side.
This always stresses the pipe flanges and cracks them. If I had a pound for every time I have seen this happen I would be a rich man.
Mikes email is:
mike@maseratished.co.uk