The Scorpion is very easy to work on and you will have very little trouble. The piston seal is an O-ring type (not Leather) and is held in place be a spring "c" type of clip. I never found that they liked long term use with an upgraded spring, so I would replace with an original type. Most of the older models that I have seen have had the piston seal seperate from the piston. This results in the piston being lodged in the maintube.
Im sure I have the diagram here someplace. I will look.