Just a small addition: Be sure to seal around the toilet and vent pipe. Since the oxygen didn't come with a shower, they didn't bother to do this. You wouldn't want to get water between the double layers of
fiberglass or under the plastic floor. Also, since the floor of the toilet sits above the main unit floor, sealing the drain can be problematic. You may want to cut a notch out of the corner so you can tighten the drain nut.
Cheers! Pete.