I replaced a rotted section of floor and replaced the flooring in a small bathroom this past weekend. The owners of the house now want to replace the 50 year old worn cast iron foot tub for a newer fiberglass tub. The only source of ventilation for the bathroom is in the middle of the tub area. Can i cut a surround around the window and replace the molding with the plastic molding? Second question is how hard is replacing the tub going to be? We have a tight budget.