Our gas furnace is 30 years old. I have had it checked and tuned up a couple of times and they tell me that it burns clean and the fan works fine, but that the bottom of the sealed pan is rusting away and when it rusts through there would be a hole where the hot (or cold) air would blow into the garage instead of the house. Today, the air coming through was warm. It's the warmest weather of the year of course. I want to check the gas or whatever is inside it to be sure it doesn't need to be topped off, and check about holes. I have heard both that they can and can't be repaired. Has anyone replaced a gas furnace lately? How much did it cost? Or did you consider doing it yourself? We have a one story house of about 2,000 sf, with a heat pump that we never use which runs through the furnace fan anyway, so we still need the furnace fans. Any experience ideas with this? Thanks!