Right on!
You need an O2 sensor. Fix it right!
I had the same code, new O2 was all it needed. Do not start cutting crap up, unless you know 100% it is gone. And you should probably replace both. Both talk to each other and if one is weak, bad or missing, the other freaks out! Monitoring gases before and after the cat.
Then you have to address the misfire. Commonly caused by bad, or weak plugs and or wires. What condition are yours in?