Hi, Cheryl. My suggestion is to remove the paneling in one room and start from there. Since you don't know really what is underneath, you will just be guessing but the ceilings should give you some clues. If they are in pretty good shape, the plaster walls should be too.
Since I don't know either what you will find, you may choose to repair the plaster. You could also patch the plaster enough to get the wall surface flat and then put up fiberglass sheeting and you can paint or plaster over that. This is a good fix if the walls are somewhat cracked and you can get the product at good wallpaper stores. You use a bonding agent that stays slightly rubbery and prevents future cracking from coming through. The last option is to apply thin drywall but you have to tape the joints and this can get messy. Let us know what you find.