In my experience the bathroom parts ~ toilet, shower pan, etc. go in first... later the walls... you can work on your floor, but to repair some items you may have to remove a lot of interior... if you need to correct rear end seperation... I would search that phrase with the search button and see what others have done... Good luck!
Welcome to the forums. This is a great place to find many answers... if you try and can't find the answer to something, post a question. You will get responses!
Mrs. NorCal Bambi (traveling in S Tardis)