Please help my 15 year olds equinox Po131 low O2

[Oneeye]

I am at a lose here. My 15 year old son just used all his money to purchase his first car, a 2010 equinox LS 2.4l. It was in a small front end accident. Broke radiator, condenser and cooling fans. We have replaced all that and now are getting a Po131 low O2 sensor code. I pulled the schematics and checked continuity and voltages and them seem fine but I'm not sure. I have pics of my findings. I am slightly concerned it is a head gasket and that is way I'm getting a misfire but compression readings came back ok and I don't see coolant getting less. I do get quite a bit of smoke out the tail pipe and it runs rough. I also changed the plugs and O2 sensor 1 with AC Delco.

 

[Oneeye]

See pics