I have taken the sideplate off a Smith & Wesson revolver a couple of times. The first time, I chipped the sideplate because I didn't know what I was doing. It was years before I attempted that again, and I was as nervous as a long tailed cat in a room full of rocking chairs when I did it. No damage that time or the next because I had taken the time to learn how to do it.
What I found those times were more or less clean internals. So I put a couple drops of oil here and there, and put the sideplates back on. Now, I just spray them out with Gunscrubber, let it dry, then a few drops of oil here and there on the trigger, hammer, and any other opening I can find in the frame.
I will loosen the screw that holds the crane in and slip the crane and cylinder out on an old used gun. That way I have another place to spray Gunscrubber and I can clean and lube the cylinder.
Funny Tuck should mention WD-40 turning the finish on a Python cloudy. I bought a rather rough looking Python a few years back. After getting it outside I thought maybe it wasn't as bad as it looked inside. My wife wanted a cup of coffee so we stopped at a 7-11. While there I bought a can of WD-40 and a roll of paper towels. I sprayed the Python with the WD, and wiped it off with a paper towel (GASP). Surface rust, dirt, dried oil and general crud just rolled off that gun. I'm not going to tell you it looked like new, but it looked a "H" of a lot better after that than it did before. A few coats or Ren Wax after we got home and it looked even better.