How do I know if my catylac converter 02 sensor needs t ok be replaced

You have a crack/split in the exhaust pipe. Seek help from a muffler shop. For a vehicle like this, I would look for a National Budget Muffler, or some type of really small chain. Buy the very minimum you can, don't go for extended coverage of anything, and just fix the broken parts. Any repairs you do should outlast that transmission. That's why I say go cheap.