How do I add schema snippets for name, author, date published, image article section, article body, url, publisher, and aggregate rating. Is their a way to access the complete source code for my items so i could add these using using by copying and pasting from Google structured data markup tool or do I have to use an extension.

Hi. Yes of course, you can change completely K2 markup by creating template overrides. Please take a read at getk2.org/documentation/tutorials/174-templating-with-k2-and-the-concepts-of-sub-templates to learn more regarding K2 templates.