Where to start with payment plugin with greek bank direct payment

[jordantsap]

I'm new to joomla or vm development and im a little stuck.
I communicated with the greek bank and they sent me a php file which looks like the first attachment below.
I need to know where to start with that meaning that i want a help in which plugin folders and files i need to create or dublicate.
Paypal plugin seems similar but not sure if it actually is.
Any help will be appreciated

[GJC Web Design]

you need to pass a configured xml via soap with the WSDL xml accessible on your site

it probably could be done by cURL as well

In process this is probably much closer to the authorize payment plugin