Pull ugly wall-like substance off walls of original bathroom. (do this only if you have another bathroom to spare) Discover that this is a very time-consuming project. Allow your wife to finish it for you on her day off after she realizes you've done too much demolition to fix it. Assure your loving wife that you can absolutely re-do this mess. Drywall isn't hard, you've been told.
Do research for several months about dry-walling and tile work. Then decide it is far beyond your capabilities to put back together. Assent to some partial help from professionals.
Schedule professionals recommended to you. Wait 5 weeks for their 3-day job to be completed. Pull up old floor so that old hardwoods will be revealed. Notice there is no old hardwood. Call in a colleague's husband for advice. Listen to him when he tells you that you are looking at asbestos tile. Go buy materials to cover old floor. Read instructions about how to install new floor. (also, be glad you live within 2 miles of both Lowe's and Home Depot)
Install 1/2 of new floor. Again, allow your incredibly patient and capable wife to finish the job. Make sure most of the wall painting happens on her day off while you're at work.
Work at your day job all weekend. Come home to beadboard, baseboards, crown molding installed by your wife with lots of help from your daughter.
Do finishing touches on walls with your wife. Be confident you can install the sink with no problem. Try valiantly for the remainder of the day. Then call in professional help.
Be very, very grateful you have a loving and understanding and talented spouse. And keep your day job.