I suspect the regulator seat oring is also bad, which is why the trigger pull is really heavy, and also why it is leaking out the back. Once you give everything a good cleaning and replace the orings, you should be good to go. Don't forget to change the bolt spring as well. It is a consumable item, so it does wear out and will cause the valve to cough and leak out the front when you are shooting.
Mags are really easy to fix. Most problems can be fixed with a good cleaning and maybe replacing an oring.
Except for the Automag in front, its usually the man behind the equipment that counts.