Originally Posted by plantsower
Before I start this, is there anything I can do to screw it up and completely brick it if I misunderstand the instructions?
If anyone tells you that you cannot screw it up and completely brick it they are lying, have no idea what they are doing, or they are kidding you and themself. However, if you follow the instructions in the order in which they are given, and do not take shortcuts, extemporize, or make assumptions the risk is quite low. Once you vary in the slightest the risk increases logarithmically.

Originally Posted by plantsower
Are these instructions the same as doing a factory reset? That's basically what I want to do, and then upgrade to Catalina for now.
The instructions I gave you will install the latest version of macOS compatible with your system, so is not a factory reset in that it will not restore it to the version of macOS that was installed when your computer left the factory. If your computer is currently running Catalina then hold ⌘R when you reboot. If it is running anything other than Catalina special provisions must be made to assure Catalina is installed, so let me know and I will give you the additional instructions. (NOTE: in that case you will need a thumb drive with at least 16 GB capacity.)

Originally Posted by plantswer
When you say "When that completes, quit Disk Utility. On the Mac OS Utilities screen select Reinstall Mac OS and follow the prompts on screen. When that completes you should be booted into a fresh copy of the latest macOS compatible with your computer."

Is there still some sort of utilities screen showing after I quit Disk Utility? I think I am getting the two utilities mixed up.
When you boot from the Recovery Drive the window that opens is the Recovery Assistant which offers four options, Recover from a Time-Machine backup, Reinstall MacOS, Disk Utility, and Safari. If you enter Disk Utility or Safari from the Recovery Assistant window when you exit them you are returned to the Recovery Assistant. If you have entered either of the other two options when they complete you will be booted from the newly recovered or installed macOS.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein