Hey Ed 🙂
We have a handy tutorial which helps set which fields you’d like required on the Community Events submit event form.
For the rest of what you’ve described, a simple template override as explained in our Themer’s Guide is the way to go. The submit event file can be found here: /the-events-calendar-community-events/src/views/community/edit-event.php.
I like to share this Customizing WordPress #1 – How To Create A Child Theme by LevelUpTuts YouTube video as it’s essentially the same process as what the Themer’s Guide entails.
Best of luck and let me know if you had any other questions. Cheers!