Ubercart - Add custom message on checkout complete page

Adding a custom message in Ubercart for Drupal 6 when customizing the message via the admin at "/admin/store/settings/checkout/edit/messages" just won't do it. Add

theme_uc_cart_complete_sale($message, $order = NULL)

in your theme's template.php file. The $message variable contains the final text about to be outputted on the screen so changing that text can challenging and changing "/admin/store/settings/checkout/edit/messages" might be what is needed. Adding an additional message before or after the original message based on info provided in the $order object is quit simple. The $order variable contains all the info about the order that was placed letting you access info needed to dynamically create messages.