I completely understand. 
It can feel a bit nervy doing the backend stuff versus the admin console.
Just to check, do you have access to your server (self-hosted), or are you using a hosting provider? If you don’t have access to your server you may need to contact whoever is hosting your site to make these changes.
If you have access to your server, I think the safer option is to re-run ./discourse-setup as you’re less likely to make a typo outside of the data you’re entering. It won’t double up your live instances, and is fine to run multiple times. 
You can refer to the Troubleshooting email on a new Discourse install guide for more info as well.
And you can also take a back-up from the command line, if you want to be prudent.
Do you want to have a read through of those and see if you have any questions before you get started?