Better still, take out the screw, open the cylinder and lay the pistol on its right side. Hold the cylinder solidly in place with one hand and pull the crane forward and out with the other. That way you have much less chance of scratching the cylinder or frame.
One more thing, make sure you use a screwdriver specifically designed for a gun. I know this sounds crazy, but Chapman makes a kit with a bit that will fit the sideplate screws on a Smith and Wesson perfectly. I think Brownells also sells a set. It will prevent the screwdriver blade from jumping out of the screw slot when torqued.
Deformed screw heads and scratched sideplates are a sure sign someone was messing with something.