The norgon ambi-catch is a drop in item, less than five minutes to install.

If you don't want to modify your safety selector, S&W set it up to be reversable. Just remove the grip off the bottom (pay attention not to lose the two springs and detents), with the hammer cocked, remove the selector and reinsert in the other side. Reinsert detents and springs. Reattach pistol grip.