integrating amCharts, how to work with external files?

I'd like to use amCharts to put some charts on my site, and I'd like to make module to contain them and provide some functions.

amCharts would like to get the data from an external file, i.e. data.php. I have no trouble making such a file work, but I'm trying to figure how to make it so that it can use the usual Drupal functions for database queries and soforth. But because data.php isn't run within Drupal it doesn't have the usual includes.

amCharts also uses an external .xml file to manage settings, many of which I would like to adjust dynamically. Same problem - I can create the file so that it changes dynamically, but it's all hardcoded.

Am I approaching this incorrectly? I'd like to do everything from .module and .inc files but can't figure out how.

I've searched the amChart forum, but no one's been doing anything with Drupal.

Any suggestions?

Thanks!