Hi Susan,
What you’re trying to do here is possible, though it will indeed require some custom coding.
The key thing is that you’re right that editing the files within The Events Calendar or Events Calendar PRO is a very bad idea – for this reason, we’ve built out a whole templating system that lets you change the display of various events templates by simply adding certain template files to your own WordPress theme or child theme. It’s really handy!
To learn about how to make these custom events templates, first check out our detailed “Themer’s Guide” to see how it all works → https://theeventscalendar.com/knowledgebase/themers-guide/?source=tri.be
Once you’re able to to do that, then displaying data from ACF fields is as simple as using any of ACF’s own functions for doing so – there’s a great overview of this on the ACF documentation here, so check this out too! → http://www.advancedcustomfields.com/resources/displaying-custom-field-values-in-your-theme/
Those two resources should get you really far along with your goal here – we only have limited support for customizations and custom code and such, but if you get stuck anywhere along here, or have any other questions or concerns, don’t hesitate to ask 🙂
Hope this helps!
George