Yes, if an automation script has a hardcoded field name, changing that field name will break the script.
If you have an automation script that gets a field value using an input variable on the left side of the editor, and the field name is not used within the script itself, you should be okay.
As for testing things, I find that testing things is necessary for being a developer. It takes a bit of experience to know when and how to create a test environment, but having a test environment is very freeing. I can wreck all kinds of havoc in a test environment and not mess up production or customers.
Thanks Kuovonne.
I hope to pick up some JS knowledge over time which will of course result in lots of testing and I'm sure you'll see more of me posting questions as I do.
Thanks for your help!