Nice find! I am the third owner of a 629-3 in the 5” classic version. I was told it had been worked over by the S&W Custom Shop, so you may want to check with the factory and see if you can send it home for an overhaul / upgrade.
Otherwise, I’ve read that a lot of the well regarded revolver smiths of the past are no longer working.
I found a website for Heffron Precision in Iowa that advertised work on S&W N frames. I don’t know anything else about them, good bad or otherwise.
I just purchased the Double D Guide’s Choice holster rig and REALLY like it for what I’m using the 629 for (bear protection while working / riding and walking around the woods).