I have a Coleman/Evcon unit that I'd like to add a/c to. It's model # 7995-656/d. Do I just need to add a evap coil? If so, which one? I don't know what size it is as far as tonnage but, it's 95,000btu in and 75,000btu out. I would think 2-3 tons would be about right. Is there anything else that I w...