Safe to try to clear 420 code myself on 2006 Element, or best to take it to the shop?

Going to pick up my Honda Toaster from the transmission shop as we speak. He discovered and fixed a cause for my gear slip between 2nd and 3rd.

But he says it's now throwing a 420 code relating to the catalytic converter. It went in with no codes/check engine light. I'm curious if he may have knocked the O2 sensor or something while working on the tranny.

I'd like to just clear the code and see if it comes back. Is there any danger to this? Or is it best to just take it to a mechanic for diag?

It is worth mentioning my caddy was chopped off/attempted theft 2 years ago. I got it replaced and no issue since. Local Honda dealership diagnosed the transmission issue which dedicated shop confirmed/fixed. There were NO codes at the dealership prior to drop off at transmission shop.