Andrew, Yes, of course Editor will be kept up to date.
Tara, if you plan on updating Editor in the future, perhaps you should make these customizations with a child theme. A child theme allows you to make modifications to the theme without them being overwritten in future updates. Here is a guide on how to create a child theme.
Ultimately, it's up to you. You can choose not to do the child theme if you don't feel comfortable with the code, or if you don't think you'll need updates going forward.