I run several versions of the store.
I have a dev version where changes can be made. If the changes pass I will install them on a test site where I can run a series of tests as admin and as users.
If the changes pass and only if 100% certain will I install them on a "pre-prod" (pre production) site. The pre-prod site is a copy of production and can always be used to compare to the production site that the world can see. Making changes to pre-prod means updating my documentation that shows what configuration settings are required and the sequence to make them + lists of all files in that change.
This is necessary so my production system has minimal down time when making changes and I know exactly what I am changing.

Before I install any updates such as the latest version of Product Fields, I compare the new version against the old using WinMerge to see what has changed.