You need a new exhaust system. I'd be surprised if the catalytic converter was bad, it is usually the muffler behind the converter that rots out. Catalytic converter back exhaust systems from Volvo are good quality and reasonably priced. Tasca Volvo has been a good online parts source for me.

Exhaust work is not complicated, it is just awkward if you can not put the car on a lift. You will need a minimal set of tools to replace the exhaust system. The best part of a complete cat back system is that you can cut up the old system to remove it.

It does not sound like you have a lot of mechanical experience so rule #1 is Don't get under a car supported by a jack, set it on stands or blocks before you start to work on it.

If you decide to do the job, post back. People here are always willing to answer questions and point out ways to do things.

Greg