Here you can see the gas piston on mine. The barrel is part of the frame and not removeable, as far as I know.
I don't know that it's gonna hurt the shooter when it gets hot. It's not like a sudden thing. You'll put it down and let it cool off before you let it burn you. I can't remember exactly, but you can probably go through four mags before you need to take a break. Obviously, you're not gonna do well in an all out gunfight with one of these, but then the magazines are so expensive, that you probably can't afford to carry more than an extra with you. It's fine for CCW, it's very accurate, easy to break down and just a cool little gun. The PSP's are very affordable. I called it my Hans Gruber gun.