I had a pool installed last year, approx 15k gallons, 33x17 sport pool 3.5-5-4 ft and at the time did not think I would need/want a heater. Now I am thinking I may want to have one added. How difficult is this to do and what might it cost? I don't know what peoples thoughts are, but I would like to get something oversized so that if I decide to in the middle of the winter want to go swimming I could get it up to a decent temp with a solar blanket on it.