Hello Glenn,
I suppose you have modified the original templates located in: /plugins/event-organiser folder. If that is the case, it will be very easy to come back to the original ones. But you have to know that even if you were happy with the results of your modifications, you were going to loose all of them, because each time that a new version of event-organiser is available via the dashboard, you are always replacing the whole event-organiser folder.
In the same way, what you have to do right now is simply replace the event-organiser folder that is online with the original one.
So, if you have the last version of event-organiser:
1. You can download the plugin from the github repository (https://github.com/stephenharris/Event-Organiser/) via the button download zip.
2. On your computer, you can decompress the folder.
3. You connect to your site via filezilla or cyberduck.
4. You replace the folder of event-organiser that is online with the one that you just downloaded.
At the same time, if your website is https://www.portcredit.ca, I really cannot see what is exactly what you consider “a mess”? I have the impression that event organiser is working well… What is exactly what you want to accomplish? Maybe I can give you some advices…