If add addons, how does it affect upgrades?

I am a new Zen Cart user. I have 1.3.8.

I have a question about adding addons/contributions. If I add an addon to admin, how is that going to affect the admin when a new upgrade is availab;le?

What would I have to do to upgrade if I have added addons?

From what I have learned so far, I can use the override for the template side, but what if I have to change the code to add an addon? Do I also add those code files to the override?

Thanks,
Kat

Most addons don't require changing core files, so upgrades won't be effected. That said, you may have to compare the files from the addons to the files from the upgrade to incorporate changes. It's not as complicated as it sounds (but it can be tedious). You an use a program like WinMerge to compare the files if you have them on your computer.

I use one very old addon which requires changing a core file. I have to make the changes every time I do an upgrade, but the addon is important to the site I use it on, so it's worth the extra effort.