I'm working on a local version of an outdated Drupal 6 site which can not be shut down for a minute. The goal is to update the modules and give some enhancements, like adding tags, making a better menu and dynamic blocks etc with the least possible down time for the site.
It will probably take a few weeks for me to do so. Meanwhile new content will be added to the production site as per usual.
My question is: When I finish developing the requested enhancements on local version, how should I integrate newly generated content to the development version before putting it online? I can not simply import the production database dump since this will undo my whole work. So obviously I need to import only certain tables. But how should I figure out which ones? What would you do in this situation?