If it is the one I think...
I still have the stock plastic grips, a damaged slide and some odd ends in a baggie somewhere. I have the bushing in there.
If it is brushed finish with some VERY large wood grips (held in place by silver screw with a purple/pink ring on each), and a bull barrel instead of the bushing style of a reg para...
Here is the last pics I had:
You would have to find a PRE-Magna WA metal chamber to install in there.
Otherwise, you would have to change the whole hop-up/barrel/rubber/chamber/outerbarrel.
I don't know about the catch, but the sticking slide is because the followers of the mags are getting worn. They have a notch grooved on the tip and this is where the nozzle get stuck. You can open the mags and file the followers at an angle so that the nozzle don't grab the edge.
If you are looking for parts, most parts made for WA will fit. Stay away from Sheriff parts. For some reason they never work properly (the hammer is a Sheriff one. Needed a lot of work to fit)