About your insulation question, yes you could benefit from insulating the cellar ceiling. IF YOU DO, make sure you put the vapor barrier facing the living space. Someone brought up in an earlier post about their cellar ceiling being insulated at some point in time where the "staples showed" this would leave me to believe that the vapor barrier was facing the wrong way! I agree with keeping moisture out of the cellar to start with but that can be expensive, do you have a dirt floor? If you do put down some 6 mil poly and some crushed stone. Insulating around the sills will deffinately help to keep drafts out.