02 Jetta Catalytic problem

I have an 02 Jetta. Receiving the catalyst bank 1 error when they did the emissions test. I told them to do a diagnostic on it to find out what needs to be done. It has 85000 miles on it. Most everyone is saying it's probably an oxygen sensor and they would replace that but if the mechanic says it's the catalytic converter, should I go ahead and replace the converter knowing it's going to be very expensive?

I've never used this mechanic before so I'm not sure if they are trustworthy or not.

I would get a second opinion. Secondly I believe if it's your convertor it is still under warranty by VW. I've had this code pop up before and it turned out to be my MAF.