Most car owners will never need to replace their catalytic converter during the lifetime of their vehicle. They are built to last and are not exposed to the same levels of wear and tear as moving parts of the car. But a build-up of rust over time and significant knocks to the underside of the car could cause irreparable damage to your catalytic converter and mean that you would have to replace it completely. You could save yourself some serious cash by installing the new catalytic converter yourself.
Read the whole article - How to Replace the Catalytic Converter