If you made changes to the source code then updating the package will override all those changes.
I recommend always following these steps
1) Make a backup
2) Remove the Opsive folder
3) Download and import the Opsive assets
It is very important that you use version control (github, gitlab, plastic scm, etc...) as this will save you in case anything goes wrong.
It would also help you know what files you changed in UIS.
After making the update try to remember what changes you made and reapply them.
In general it is recommended to only change the source code if you do not plan on upgrading, instead you should inherit the classes and make new custom scripts to replace them, this way you never lose your changes when updating
good luck