Hi all. We are considering buying a good-boned Cape Cod in Louisville KY and want to fix the upstairs ceiling. There are just a few real cracks/weak spots and plenty of very fine spider webbing and it is sagging between every joint. While keeping the plaster isn't essential to us, it would be nice. Estimated at 400 sq. ft., any guesses on the difference in price between a thick skim coat and sheet rock replacement? I'd assume it has never had any work, would it need re-lathed? Thanks.