Its value to a collector is reduced. Its value as a shooter / carry gun might actually be enhanced since nickel stands up to holster wear, etc, better than the original blue finish.
As for guesses about what it might sell for on say GunBroker or the like:
We usually say that any N-Frame in working order is worth $500
Add to that it is a 4" (usually worth a little more)
It is an earlier model / S serial number (usually worth a little more)
It has very nice / desirable Target Stocks that could bring $100+ just by themselves (it would help to see the other side)
My guesstimate is a rock-bottom price of $600 with the stocks, but probably $50 to $100 more to the right buyer.