It depends on the size, the amount of mold, and the type of finishes you are planning on adding. Consult a local service company (for Mold) if it is extremely bad. BUT REMEMBER, tearing out sheet-rock and putting up new sheet-rock will not fix the problem. First, you need to know the problem, what is the source of the water and how can it be remedied? If you don't do this first, you are wasting your money with the "redo" work.