Catalytic Converter and O2 sensors, Replace? Options

[BlackSTX]

Alright. My car hit 100,000 miles a couple of weeks ago, and about 60 miles later my check engine light comes on. I take it to autozone and the code reads "8420- Catalyst system is not performing to minimum specifications-bank1" or something like that. The dude told me it sounds like the catalytic converter, which I agree with, and that it means it's the first one (the bank 1 part). So I take my car to the local exhaust shop, and they recommend changing the catalytic converter and both O2 sensors for $550. They didn't even mention a first or second catalytic converter. Does anyone know if it's the first ro the second? How hard is it to change the sensors and cat? Can they all just be unscrewed? Also, what is a reasonable price for each. Autozone quoted me 125 for the sensors, and the muffler shop 130. What about the catalytic converter, and where could I get one of those? Would I need to lift my car to replace it?

[BEEFSTEW800]

dont get a universal because they dont last long (about a year) and the only reason the shop told you to put in the o2 sensors as well is because that is the "easy" way for them to fix the check engine light (they dont have to diagnose anything). if you do have an inefficenty code then you will probably just need to replace the cat.