Curiously, how much would something like that cost from S&W?
While S&W would have to estimate, which they will (in writing), I have always been surprised how reasonable they have been on some pretty serious work.
My guess (just a guess) is that it would be much less than $150, return shipping included.
Call their Customer service and discuss, keeping in mind that they will need to have the gun in hand to do an accurate estimate.