I've been searching everywhere and there seems to be very little about Zen Cart... at least anything much deeper than "install and go". I'm skinning (templating) a Zen Cart store, but the design I want doesn't fit in with the current layout, so I've had to make extensive changes to tlp_header.php, tpl_footer.php, tlp_main_page.php, etc.
Is there a reference out there that shows how to do basic things such as grab all of the categories and their thumbnails, list all items in a category, etc.? I checked out the API Documentation but it's confusing as hell.