Cold setting is very easy. I would not hesitate in doing it. Sheldon (pbuh) is correct that the one size jump won't cause any problems with dropout angles, but depending on your frame, you might only move one arm. I had this problem where the right side moved 3 mm and the left only moved one.
If you are worried about cold setting, an LBS could do it for you. Usually this is the same price as a frame straitening. We charge $25 for it.