Catalytic Converter DIY
 

After loaning my 2003 S60 (80k mi.) to my brother, it revs much louder now. (I'm not even going to get into his driving record or why I let him borrow my car, so please don't ask) My check engine light has not turned on. I walked around and saw my tailpipe was a little lower than it should be because the welding broke in back. After a quick coat hanger fix of the tailpipe, I took it in to my neighborhood shop and was told the "flex" part of the catalytic converter aged, wore, and is broken. I was quoted at $800 ($600 part/$200 labor).

My questions are:
1) Is this likely even a catalytic converter problem? (I haven't taken a look myself. How would I test it?)
2) The flex part is just a pipe, not part of the "converter", right? If so, can I patch?
2) If I need to replace the cat., is it an easy fix to swap in a new one?

Many thanks for any feedback.