G'day Rc1700.
Remove the four nuts that hold the lift piston assembly to the cover and either borrow or buy a stud driver ,a tool to remove /fit studs or use two 1/2" unf nuts and double nut them onto the studs sticking out of the cover ,if/ when you have the four studs removed the lift assembly will become loose and allow you to remove the cover then when it is off you can easily remove the broken bones ,it may be that all you need to buy is a new piston ,rings and a new cam arm,when you have it in pieces I will guide you through the reassembly and readjustment of the hydraulic system.
Don't be concerned it is not really a big job.
ooroo .
Hutch.