08 Prius Failed Cat?

I own a 2008 with just over 200k miles and purchased the vehicle in 2010 with 75,000 miles. Recently I took it upon myself to replace the iridium spark plugs, pcv, and ws-atf, as well as clean the sooty throttle body & mass airflow sensor. I must assume that the maintenance stated above had never been performed prior. A few days ago I brought my prius in to have both coolants flushed and bled at the dealership. I also had them run the CEL which has come off and on for maybe the last 30k. They told me that the catalytic converter is clogged and must be replaced for 2k+. I have not experienced any egg like smell or notable loss of power OR mpg. The only thing I have noticed with the car is occasional rough engine cutoff/startup. My prius also does not leak/consume any noticeable amount of oil between 5k oil changes. Should I replace the O2 sensors first? I have looked around and am seeing direct fits for about 300 online. Hopefully someone who has had similar issues can chime in. With so many high mileage drive components I refuse to replace with toyota oem converter and am not concerned about the aftermarket converter possibly tripping the CEL I'd just like to ensure my engine isn't fighting back flow pressure from a clogged cat. I'd love to keep my prius running for another 100k or so.

Thanks in advance guys!

- Noah

 

Yes indeed the code was P0420, along with P3192 (couldn't find anything on this?) What is required to check the sensor values? I am by no means mechanically proficient, however find most general maintenance simple by nature. Should I get a local muffler shop to check the sensor values?

 

Yes, those two codes are listed on the receipt. Maybe the dealer meant 3191 or 3190, something along those lines. I suppose I can have it rechecked for free at the local auto parts. I was reading that either 3190 or 3191 is reduced engine power.