Owning a 6906, the only work I felt it needed was some polishing to remove the gritty takeup in the (DA) trigger. It was dragging across something, sear legs, disconnector? I forget... but whatever it was had some rough toolmarks on it. Oh, and I also hacksawed off the hooked "finger rest" magazine base pad. I don't like hooked finger rests on a CCW gun, they catch on too many things.
In my opinion the S&W 3rd gen autos are underrated, and I never understood why folks will bitch about the slide-mounted safety (which is almost identical to the Beretta's), and the magazine safety, which, like the High Power's, can easily be removed.
I have been keeping my eyes open for a 3913 in good shape, but haven't seen that many. I'm not willing to pay over $350 for one, which should be reasonable.