P0431 Fault Code Explanation for 2001 VW Passat GLS Sedan

I recently purchased a 2001 Volkswagen Passat GLS Sedan with a V6 engine and automatic transmission, on August 10, 2010. Yesterday, my check engine light activated, and after taking it to the dealership where I originally bought the vehicle, they diagnosed the issue as OBD-II fault code P0431. Based on my research, this code typically indicates a problem with the catalytic converter's efficiency, specifically in Bank 2 of the exhaust system. Possible causes include a faulty oxygen sensor, an exhaust leak, or a failing catalytic converter itself. As someone with limited automotive knowledge, I'm concerned that the dealership might be recommending an expensive repair without clear justification. I'd like to understand what exactly P0431 means and whether common fixes—such as replacing the oxygen sensor or repairing an exhaust leak—are valid solutions. If the issue is a catalytic converter failure, can it be replaced? And if so, would that resolve the code? I'm seeking factual information to help me make informed decisions about what the mechanic is suggesting. Any insights or real-world experiences with this code on a 2001 VW Passat would be greatly appreciated.