well you have 2 options. first is replace it with a factory Cat. that requires you unbolt the cat from the manifold (4 bolts 13mm IIRC), unbolt the 2-bolt flange mid-way back the exhaust and unbolt the strap around the Cat. then you can lower the Cat and replace with a new one. the other option is take the cat off, turn it upside down and punch out all the material thats in it then reinstall the old hollowed out cat. you will have to get/build an MIL eliminator for the downstream O2 after that though and if you have emissions testing you wont pass the sniffer test.