Stucco is a portland cement product and can be very resiliant in moist environments. Adding acrylic fortifier (Quikcrete) makes it more waterproof and improves adhesive properties. It may be a fine wall surface, but you may need a lath system to attach it properly. Applying stucco is not necessarily an amature proposition.
Frankly, if you are simply looking to resolve a very uneven wall, it is easier to demolish the wall and install new drywall. Use moisture resistent drywall (greenboard). The cost is not very high for this project, and when you are done you have no limit to decorating possibilities. Hanging drywall is a great DIY project and requires few tools. You should be able to handle it for a small room. If you have showers or baths, you may need to tile or attach an alcove. Installing drywall will give you an opportunity to inspect electrical systems, insulation and plumbing and make updates as well.