I've been meaning to do this for a while except I had a problem (more later).
The pistol is one of those designs that the trigger mechanism is really better off being left alone other than a bit of a scrub with some cleaner (meths/isopropyl alcohol) and then some lube. This is partly because it would be very fiddly and partly because you cannot get spares.
Firstly I removed the rearsight by undoing the 2 cap head screws on the side of the sight and lifting it off the grooves.
Mine did not have a silencer on it and I did not have the special tools that I think the gun came with. I used a flat headed screw driver to undo the barrel and it came out ok.
I then pushed the button on the RHS that you use when cocking the gun. This lets the cylinder spring up a little from the trigger and grips. If you undo the forked nut on the grip/cylinder pivot, the pivot screw will come out and you can then slide the grip back a little and lift the cocking arm out of the cylinder. Put the trigger and grips to one side. The sear is in a little housing welded to the cylinder and is a simple thing with 1 pin and a coil spring. Remove the pin and the sear and spring slide forwards and out.
You should now have the cylinder, end caps and shutter mechanism left. There is a plain circlip holding the end cap/loading shutter--it was a bugger to get out. I managed by grinding a small screwdriver so I could get at it. TIP when I got it out, I ground either end of the circlip so it had a "lead in" to make it easier if it needs doing again. The endcap/loading shutter then came off and the little shutter/transfer port thing lifted off the end of the cylinder. There is a flat section circlip in the endcap,which opens and closes the shutter when the endcap is twisted.
I then wanted to remove the inner endcap from the cylinder to get at the piston. IT WOULD NOT SHIFT I tried Plus gas, tried to make up a tool like the proper peg spanner etc but it would not shift. I sent it to Mick T20 who managed to get if off without damaging it. nut sure whether he made up a peg spanner or a soft bush to grip it.
Anyhow, with this off, the piston, mainspring and guide came out. Clean and lube everything and go to part 2