Extending functionality of Classifieds

My question in a nutshell is that I'm trying to make the parent categories on the sidebar (Tag Cloud Classifieds Widget) into a drop down option menu, where I can display the child taxonomies based on the option selected (either via ajax or just get all of them at once and choose which to display with js). How can I extend the plugin with my own custom plugin, and is there a codex of functions available for me to use?