Best Practices for Classifieds template changes and style questions

I have two questions.

1. How would you recommend someone develop a template for your classifieds. The shortcode for the list page is too limiting. I want to develop a more robust list page, but don't want to update the plugin some day and overwrite changes.

2. Where would you send someone to start looking at attributes such as adding the total # of posts for a specific category. I'm trying to figure out where the different attributes are in the code if I'm going to start a template. See attached image for what I'm trying to achieve.