I searched for some documentation but didn't found anything. Then I've looked in scripts of existing modules and still need some help because I don't have much time:

1. which script is calling the URL that process the payment?
2. how the gateway returns the data back to OSC and wich script handles that data?

Is there any UML or some kind of diagram for payment process?
I'm also willing to pay somebody to do it for me.

Thanks.