Toyota Repair: catalytic converter, toyota corolla, trouble code

Question
2000 toyota corolla. The engine block light came on. Mechanic said the up sensor in the catalytic converter wasn't functioning. Need a catalytic converter. Said only dealer has part. The light still goes on and off often. What do you think?

Answer
If the catalityc converter is the problem and you are residing in the US it is covered under the federal emission control warranty for 8yrs or 80,000 miles, it would also help if you could tell me what the diagnostic trouble code(s) were that caused the check engine light to come on, with that information I can be of much more help.