Was it closed and properly cared for during those 16 years or was it basically abandoned to Mother Nature the whole time??
If no one took care to keep it properly closed during that’s time, then freeze/thaw damage is quite possible. That can affect everything from the structural soundness of the shell to the integrity of the underground plumbing.
So, at Alan stated above, if the shell holds water and plumbing is sound, it should be easy to get going while decide on how you’d like to remodel it. If it can’t hold water or the plumbing is shot, then you’ve got a lot more upfront work to do on it before you consider any kind of remodel and equipment changes.