I'd isolate the machine from the internet, change my passwords from a trusted machine, save the media and documents from the isolated machine, and then reinstal

I'd isolate the machine from the internet, change my passwords from a trusted machine, save the media and documents from the isolated machine, and then reinstall the OS / factory reset the isolated machine. Still, I'm sure that there are technical possibilities that this doesn't account for, but I think I would be okay with the procedure nevertheless.