I am a typical handyman and have done countless jobs over the years. Several years ago I began remodelling out bathrooms. I came within a hair of doing the tub in the first bath. The thing that made me hesitate was the fact that we were installing a marble tub and I was unsure of the soundness of the subfloor. To make a long story longer, I hired a "pro" and am grateful to this day. When I saw what he did I realized that what he had that I didn't was knowledge. I spent my time doing the things that I knew how to do (tile, install cabinets, paper, etc. No regrets. If you do undertake the project you already have some good advice. Good luck.