Sounds funny to me. Exactly *why* does the gun allegedly need a new firing pin? My agency had a bunch of them; I have used these guns hard for over 20 years, plus I had Ruger's armorer training on them and the GP-100s. Never, ever heard of a firing pin problem of any type whatsoever.
If you are getting light hammer strikes and misfires that is likely a spring problem. Post your situation here and we may figure something out. Alternatively just box it up with a note and ship it in to Ruger. They made it and they know how to fix it. Replacement of a firing pin is a factory job anyway, and I doubt they would supply the part to anyone outside in any case.