Not exactly sure what negitive effects it has on accuracy but Ive heard that it is not a good thing to help with accuracy , I'm guessing that the new desgine has a heavier firingpin which slows lock time and thats a bad thing in most cases and as for most factory firingpins its a sloppy fit.
As for changing it yes it can be done , their are several replacement shrouds on the market , but for the money I'd go with the whole shroud pin replacement setup from Gre-Tan , it comes with a new light weight firing pin , tight spring and new replacement bolt shroud that Aluminum the whole setup drops some wight from the gun and makes for a better fitting firing pin the cost is around $50 or so and its a simple at home swap