Good evening Aaron and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
I would love to help you with this topic.
That is a great question.
As a precaution, I suggest backing up your Database before doing anything (just in case).
Normally, our CSV importer should do just that (update the events when reimporting).
In the odd case it does not (and creates duplicates), I guess you could simply delete all events and just run a basic CSV import.
Let me know how that goes.
Best regards,
Geoff B.