Do I need to add something to the DOM to get the “Example - Custom Google Mapping” to work in my solution? Also I am not needing direction routing service, just multiple markers on the map.
Yes, the Google API script does need to be added to the DOM in your site settings. It looks something like
<script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY_HERE"> </script>
but with your API key, of course