I've spent the last few days fixing some of the code in the pay_node module, but I am now realizing that the module was never ported to Drupal 7 and that is why things mostly don't work. Since I have never used pay_node before, I'm not sure how it is supposed to work, so I am installing the Drupal 6 version now.
I could use some help with porting over parts of pay_node if anyone wants to help out. Specifically, I'm having trouble getting the embedded forms (from the donate module) to register payments towards a specific node. They payment is made but it does not track in the DB that it was made towards a particular node.