Firmware and safety questions

I have had a CR-10 for years now that's still almost completely stock, I honestly don't even know what model it is. At some point a buddy of mine really scared me about thermal runaway protection and I quit printing for a while planning to look into updating my firmware and then I just bought a resin printer and that was sufficient for most of what I needed. Years went by of my CR-10 only being used for small projects very occasionally. I now have a project that is going to have some multi-day prints. I have no complaints about the print quality, but I have no idea where to start with firmware. I still have the stock installed.

Can anyone direct me to what firmware I need to be using, and hopefully something that can explain to me like I'm five how to install it? I'll probably never leave it running when I'm at work, but I currently don't even run it overnight. I'm sure a lot of that is paranoia, I'm probably way over-cautious, but I'd like to do whatever I can to prep for safety with this project.

I have one of those foiled lined "fireproof", but probably not at all, enclosures for it that I've never actually put it in and I'll likely use that as well.