I have a furnace that is about 20 years old. The Heat Exchanger now has a crack. We are selling our home and need assistance ASAP to see if we can find a replacement heat exchanger anywhere. I have the model and serial number available, but am unable to find where to go to see if anyone carries parts for older furnaces anymore. I don't want to get a new furnace if I don't have to. Any help would be greatly appreciated.