I've managed to remove the ring clips from one side of the MCAL as I await delivery of the brass replacement pins from Forbeskm. Do I remove the piston and just take a mallet and punch the pins out? Do I need to worry about pressure from the main piston spring? Thanks in advance for any assistance.

Since no one answering, pretty sure you have to worry, I don't have this machine, but I think you want to remove the group screen and compress the piston/spring in some manner (e.g. with C-clamp or equivalent) until the lever is loose, remove the pin, then carefully decompress the piston/spring or pretty sure it will come shooting out when you remove the pins. Someone correct me if that is wrong for this machine.