SKS is a proven combat arm and a great NY legal option. Unless its damaged or otherwise deformed nothing needs to be done with the firing pin. Just ensure the firing pin channel is free and clear of debris and schmutz and keep it clean and ot will be fine.
The only problems I've had with mine, I blame on TulAmmo. That stuff runs really dirty it seems. In under 1,000 rounds of that stuff I had one stovepipe, one double fire, and a squib load (a squib load!). After I stopped using TulAmmo, I have had zero malfunctions in the few hundred rounds I've shot since, even while running it fairly fouled up.