Other companies besides Wolff market reduced effort hammer and rebound (trigger) springs, so let me make it clear that I don't prefer one over the other...I just have the Wolff product in mine. Basically...it is a replacement hammer and trigger spring that will lighten the trigger-pull. Some folks do not recommend it for fear of light-strikes, but I have never had an issue in any revolver in which I have installed reduced effort springs. If the gun is clean, rub-free and in good shape...reduced springs are usually non-problematic and will lighten the trigger-pull.
As for the center-pin spring, if you open and close the cylinder enough on a AirLite or Airweight revolver...you will see a wear-line or trail where the center-pin cuts a ever deepening gorge in the recoil shield. Smith puts the same center-pin spring in all the j-frames....from the magnum on down to the 317. The magnums and the people that shoot a lot of +p or +p+ ammo, need the pressure from this spring to keep the gun from "shooting open" under recoil. However, I have (without incident) put lighter weight center-pin springs to reduce the pin-wear in the recoil shield of alloy framed guns. It's a matter of removing the extractor rod and replacing the spring.
Yes...many shooters recommend not doing this as well, but I hardly think I will ever be able to cram a 357 Magnum or 38-Special round into the chamber of a 317. It also makes it much easier for the wife to open and close her little gun.