Just taken my Omega apart to fit new spring and service. Trigger needs to come apart and cocking link removed to get the piston out. I removed the barrel pivot screw so I could detach the cocking link .
I found the trigger assembly to be a piece of cake to assemble [though I have built a kit car or two] and generally much easier than that on an Original mod 50 which is not difficult just a fiddle to hold together .