It’s not a necessary upgrade. If you’ve already made changes to your css then there’s no need to upgrade it since replacing the file will only override your changes. https://appfinite.com/changelog/epik-log/
Looks like there are some 1.4 features that would be helpful for future mods on my site.
I believe style.css and functions.php are the only files I modified. I have the original (1.3) versions of these files. If I was to do a compare of the originals vs. my modified versions, that would at least point me in the direction of all the mods I made. (again, not that many; my site is still pretty simple).
If I could compare the original and modified versions of the files, I should be able to re-customize version 1.4.
BTW – When I created the site on Epik, I purposely tried to limit changes to the child theme as much as possible. Hopefully that will make this pretty straightforward.