The old furnace needs to be replaced very soon. I now have oil heat. I want to replace with either gas or a heat pump.I live in the Seattle area. I"m confused as to the best way to go. I would like to have heat and air conditioning My house is 3500 sq ft. Any opinions would help. I need the most cost effective unit as I hope to retire in the near future. And as alot of people are finding out It wont be as rosey as I once thought it might be. okbye JP