Beware the piston assembly bolt. Also the trigger housing screws mentioned in the disassembly video.
It's a 17mm, NOT a 10mm as mentioned in the video. Large and fragile because it is hollow. Crossthread it and you'll ruin the rifle.
If the rifle has never been disassembled, the factory assembly lube has likely turned into brown varnish that behaves like glue. Soak the bolts and screws in Kroil, which you can clean off later. Use a torque screwdriver or breaker bar with a slotted screwdriver head on the trigger, and a long-handle pattern open-end wrench on the bolt. Then while it's apart insure all the threads have clean thresholds and turn freely. Apply a dab of lube. It'll make assembly of that bolt under spring tension a bit easier.