Jim - no need to change lampholders unless the old ones are loose or broken. The ballast type is dictated by the lamp type. If you are using an F32T8 lamp just look for a ballast rated for that lamp. The info will be on the ballast label and should be on the box. As far as putting insulation over the fixtures, don't. Heat buildup in the fixture will shorten ballast life and may reduce the light output of the lamps.