The quick change above is a good mod for sure. If you could upload a pic of your PGP it could help us to help you more.
One thing that will help with smoothness to watch out for is where the lug connects from your bolt to the hammer in your lower tube. Where it hits the barrel tube in its foremost location there tends to kick up a burr into your barrel and it will rub badly, this is the main thing to look out for IMO to keep thing's. smooth. If you have a new style PGP you wont need a special tool to remove the valve body. I prefer the cartridge valves in the newer Sheridans, they are much easier to work on.