Hi Travis!
Thanks for reaching out to us!
First, please let me note that we are fairly limited in how much support we can give for custom development questions like that.
That said, we always like helping out and at least point users into the right direction as much possible.
You can only make a template override of the templates files that are indicated in our Themer’s Guide > https://theeventscalendar.com/knowledgebase/themers-guide/
If you want to customize the Render.php file you should do so by using the filters and actions available in it. This could be done with some custom coding in your theme’s functions.php file or inside your own custom plugin.
I hope that helps. Let me know if you have any follow up question.
Best,
Victor