I just had an estimate for replacing my old oil furnace with a new 85% efficient gas furnace and a separate hot water tank. The lower end was somewhere around 7,600 (6 year 40 gal water tank). The higher end was a more efficient water tank with a lifetime warranty and it's around 9,400. Both estimates include removal of my old oil tank and the old oil furnace. Is this a fair estimate? I feel like its really over-priced. But I know nothing about this stuff, so I'm looking for some expertise here. Thanks!