I would like to begin by addressing the mold issue. Mold issues, when left untreated, can affect your health and emit toxicity into the air especially in enclosed areas such as a bathroom and should not be ignored.
To ensure the mold has been removed in its entirety, you will need to begin by inspecting the entire wall cavity once the drywall or wall coverage material has been removed, making sure that the entire wall cavity is treated properly. I would highly recommend seeking out a licensed professional trained in mold removal to assist with this repair.
In order to determine how you will handle the damage, the following must be assessed. For spaces one inch in diameter or larger, the drywall must be replaced at least 4 feet up from the floor. If the drywall is above any tile, the drywall must be removed and replaced at least 12 inches in height and 16 inches wide in diameter. After you have removed the appropriate amount of drywall, you will need to inspect behind the wall for further mold damage. If there is further evidence of mold, you can treat the area with a one to one ratio bleach to water mixture and let it sit for 24 hours.
There is a mold retardant drywall that can be used to replace the old drywall to help prevent future mold issues such as: DensArmour. To prevent future mold issues from arising, you can paint with KILZ, which is specifically designed with retardant formula.
For more information on the effects that mold can have on your health, please visit these two EPA website links.
Because your question was cut off by the server, I encourage you to ask any additional questions in the comments below and I would be happy to reply with a more accurate answer to your question.