I have a 12 year old Ruud furnace that has cracks in the front plates of the heat exchanger. There is also some rust in the heat exchanger. Two technicians have told me that the furnace must be replaced.One technician told me that Ruud has a kit to fix this problem because it is a typical problem. I didn't purchase the furnace. It was in the house when I bought it. I don't know what to do. Repair it or replace it. Some people think Ruud furnaces are cheaply made. This shouldn't happen after 12 years. Help!