Karen logic says, replace the whole furnace. Why would you want to install anew part in a 14 year old clunker? Ok let's weigh out the 2 options. say u went with the new heat exchanger. The labor involved would be close to a new installation. At this point you may wan't to upgrade to a higher AFUE furnace. See what fits your budget. If you can get a newer hi-effiency furnace. It might not pay for itself right away, but down the line (let's say 2 to 3 years) the cost and your fuel bill will diminish. Get 3 estimates from reliable heating contractors. On the estimate, see what make they plan to install. You can actually save money if you do some homework. best of luck karen, Tom