No -- all you need is a hand drill and a hammer. Drill out the pin that holds the piston onto the bolt carrier, unscrew it, screw the new one on, then drill the new hole, insert a pin and peen it over. Start to finish, the whole process takes about 15 minutes. You can either get a specific pin for the piston 3 mm), or you can use a small nail.
There's a guy called Hotbarrel over on Gunco.net that sells US-made gas pistons for $15 each (delivered). I got one and it very well done (it does has the grooves, though, not the smooth head).
Easy and permanent.
As far as the trigger -- it