Kathy, if your present drywall is in as bad condition as you say, you may be better off applying a new layer of thin drywall. Sounds like you will not have to do the ceiling, which can get tough. The walls are pretty easy to do but do require 2 people to move the sheets of drywall around, not because they are that heavy, just bulky to handle. You can get 1/4" drywall and, if your present drywall runs up and down, run the new layer sideways over that. Some people like to start from the top and others from the bottom on this. Either works. If your old drywall was 1/2" thick, use 1-5/8" screws for this. mark the stud locations on masking tape on the floor and ceiling before you start so you will know where to run the screws. When the new drywall is up, tape, mud, sand, prime and paint or paper it. Sanding relatively small areas of drywall mud is a lot easier than big areas to get smooth and flat.
Don't forget to add extenders to your electrical boxes after it's up. This may sound difficult but it isn't.