Try hitting up eBay for both the cat & O2 sensor. You can pick up a BOSCH universal O2 sensor for roughly $50 +/- on eBay. Any competant muffler shop can cut out the old catalytic converter from the existing pipe and install a new one instead of replacing the entire exhaust pipe. However, depending on the price of the cat you purchase and the shop's labor costs for the R&R, you may be able to get an aftermarket pipe w/ hi flow cat for close to the same price, depending on brand...