Read this to understand what is going on and what is needed to troubleshoot your P0420 code.
http://www.autoserviceprofessional.com/ ... -p0420-dtc
With that many miles on your Vibe there are a lot of things that could cause that code and I would guess that you have more then one problem now. Driving after the check engine light came on for 10,000 miles is never a good idea as other systems can be damaged.
"If there are any misfires, ignition, fuel and/or intake problems, these must be repaired before the Catalyst code is addressed. Any misfire, ignition, and/or fuel system problem will quickly ruin a Catalyst. They are often the cause for code in the first place."
Hold on to your wallet and good luck.