Yep, there's loads to read!
http://docs.moodle.org/en/Developer_documentation
Look at the articles in the "Guidelines" section and the "How you can contribute" section. Specifically, this article: http://docs.moodle.org/en/Modules_%28developer%29
http://docs.moodle.org/en/Developer_documentation
Look at the articles in the "Guidelines" section and the "How you can contribute" section. Specifically, this article: http://docs.moodle.org/en/Modules_%28developer%29