My best advise is to turn to Brownell's.
Buy a copy of Jerry Kunhausen's book on gunsmithing the S&W revolvers.
Buy a S&W screwdriver set. I think they sell a small set just for S&W, not the big set like I have.
Buy a square or triangular ceramic stone.
Buy a spring set.
With the above, plus whatever lube you like, you can do a very good job yourself.
Mostly, you need to polish a few parts like the rebound slide, and replace or alter the rebound spring.
I usually don't replace the mainspring, since I want a SMOOTH trigger action, not a lighter pull that may not be reliable. Lighter hammer strikes are OK for target guns, but not for defense guns. Replacing the rebound spring will give a lighter pull, but still have plenty of primer popping power.
Again, you want a smooth pull, with no stacking, or "lumps or bumps".