Please excuse my lack of knowledge in the field. I have an all electric system in my townhouse. We got a new heat pump installed about 3 years ago by the previous owner. The inside unit (what do I call this? Air handler?) is as old as the house, built in 1987. I figure it's time for an update. What should this cost me? What do I need to ask when calling around? Is there a way to see how efficient/inefficient it is running? Thanks.