2003 Toyota Camry Check Engine Light

2003 Toyota Camry 4 cyl Automatic 170000 miles

My check engine light goes on and off and has for a long time. I had it hooked up to a machine to test the sensor at Auto Zone and the code came up was related to exhaust. I was advised it was probably the front catalytic converter that needs to be replaced. My car runs very rough compared to when I bought it, and I put a lot of miles on it every week. I was wondering if there are specific signs that point to the catalytic converter needing to be replaced and also if this will help my car run more smoothly?

Thanks!