DTC's NEVER say to replace a part, they tell you what area a problem was detected in. P0430 indicates that the catalytic converter efficiency is low. This can be caused by any one or more of several things. It must be diagnosed properly before replacing any parts, unless money is not an object, in which case, start throwing parts at it, you might fix it, eventually
When the ECM checks for catalyst efficiency, it relys heavily on oxygen sensor data, (especially the sensor after the catalyst) but it also relys on things that can affect oxygen sensor data output too. If a sensor supplies incorrect data, converter efficiency DTC's can be set. The most common causes are poor electrical connections, exhaust leaks, faulty oxygen sensors, and a faulty catalyst. Those are the basics to check first.