I normally polish the rebound slide on all my S&W DAs with a stone and then a light cotten cloth and mother's mag. Most everything else I leave alone, except the springs, which I routinely replace.
Polishing the sides the rebound slide is OK, as there is a limit to how much damage one can do -- though usually you will get more bang for your effort by polishing the frame and side plate raceways that bear on the sides of the rebound slide.
Polishing the bottom and, particularly, the top step of the rebound slide should be done with great care, as removal of metal here can alter critical dimensions and affect both function and safety.
There are really only two springs that might be replaced. Using a lighter mainspring in a K, L or N-Frame revolver can reduce DA trigger pull weight, but if over done can also lead to light strikes and, in N-Frames, to damage to some parts on guns that are used for fast double action shooting. Using a lighter rebound slide spring can reduce SA trigger pull, but if over done can lead to both function and safety issues.
I should have added to qualifications to my priors:
1) Armorer training does not make one a gunsmith. (The general distinction is that an armorer for a particular class of firearm is qualified to disassemble and reassemble it, observe parts that need to be replaced, and replace parts that do not require substantial hand fitting. A gunsmith is one who is qualified and equipped to make parts or alter the physical shape and dimensions of parts.) I am not a gunsmith.
2) All of my comments are based on pre-MIMS S&W DA revolvers. I have examined some "modern" revolvers, and observed some similarities and some differences, but I wouldn't touch one and do not consider myself to be even armorer qualified with one.