You should now be able to unscew the end cap, using a large screwdriver at first and then your hand (remember to keep pressure on). When it unscrews, you can remove the guide, mainspring and piston. The piston head is a parachute washer which just seems to locate on a spiggot. The piston has slots on both sides but only one notch for the sear so make sure you put it back the right way round or the gun wont cock! The cocking arm slot would benefit from a bit of light,filing and polishing. Clean and lube. Replace piston (right way up), mainspring and guide and screw on endcap. I used a rigger glove to push down on the cap. Tighen the cap up but use a small screwdriver or pin to feel for the hole that the little pin locates in and then replace this when its lined up. Replace cocking arm in its slot and then replace the barrel and locate pivot screw and lock screw. Replace the pin at front of the trigger housing that keeps the cocking arm pushed down. Replace action in pistol body, making sure trigger spring does not come out and locates in the recess in sear. Replace two screws and the nut in the pistol grip.