Insulating wartime home?

Just wondering I have a lot of heat loss on the upper part of my home it is a wartime home slanted ceilings in the rooms on the second floor I've noticed on the outside of my home that the snow is melting in those area's is it correct to remove the drywall on the ceilings and add new insulation and vapor sheet the ceilings and outside walls? just don't want to spend money for nothing or do something that could cost me big in the long run.