2009 Chevrolet Malibu Catalytic Conver is Plugged

My car one day suddenly lost power as I was passing someone on the road and my check engine light came on. I was able to make it home. Went to Auto Zone to do the free engine check and it obviously didn't tell me much but I did buy the gas additives because I had no other way of getting to work without my vehicle. Bought it to Firestone to get the light checked because my car was working better, there were random moments where it would lose power when I pressed on the gas to accelerate and it would eventually accelerate after a delayed few seconds, but still my light was on. They checked it and said I had a plugged catalytic converter. Well the guy told me it can cost up to the thousands and I just didn't have it at the moment. So now that I can maybe manage, I'm wondering what I should do about this converter? Should I call Chevrolet and ask them am I still under warranty (I'm sure it's not), but I'll check anyways. What type of shops should I call because I not only need a new converter I'm assuming but I have to get the check engine light off too because low and behold my inspection sticker is due. What are the estimated costs for the converter and labor? I was in an accident with the muffler in November, and had got about $1500 worth of engine work done right around that area because I hit the metal entrance coming from the ground where the city septic tanks lead too. Should I check with the people who fixed my car during that accident to see if I'm possibly covered for this problem? It's only been about 6 months since the car was fixed? If I got an estimate for $1200 is that too much? I thank you so much in advance for any advice or help given because I have never heard of this and am very unaware of these types of situations. I thought I had been doing right by my car but maybe not. Thanks again. Looking forward to hearing from someone.

Deshauna