acus2k

So lately I've been hearing a weird noise from the cat in MY06 and I thought it was busted. Today my CEL came on so I took the car to Honda just to get it checked and such. He pulled a P0139 which indicated that the secondary o2 sensor was messed up. He said my cat didn't pull a code so he thinks I ran over something and my heat shield is bent into the cat and vibrating, thus the noise, and my o2 sensor was also damaged when it ran over something which is what is throwing the CEL.

My question is does this require me to most likely get a new o2 sensor and heat shield? Or would getting a TP or HFC make these unnecessary. I haven't really modded much but am not opposed to getting one of these. Right now I have a stock exhaust and K&N fipk. I just am unsure what I should do...

btw the service manager also told me that I could drive around just fine, but that my gas mileage would suffer, is this true? Thanks for the help