If you hire someone to do it, make certain they know what they are doing. If you do it yourself, all you are wanting to do is to get rid of burrs and smooth machining marks a bit. I understand that parts like the trigger, hammer, etc. are surface hardened, and if you stone through that, you are left with a soft surface that will wear quickly, and soon become unserviceable. Also, make certain to not change the angles on any of the contact surfaces. Taks your time with a quality fine grit stone and give it a shot. There's really not much to it. If you look in the gunsmithing section here: S&W-Smithing, you'll find more information than you'd ever want to know, from some of the most knowledgeable S&W nuts in the world. Click on th FAQ at the top of the page, and you'll learn everything you need to know.