Using XML Gateway

We invoice and pay over 16k invoices a year between two subsidiaries that are on the same instance and are only separated by operating units.  We were wondering if the XML gateway was a good option for us to get invoices out of receivables from one operating unit into the payables module of the other operating unit.  It seems like this would be easy, since we are both sides of the transaction from an Oracle standpoint. 

Is XML gateway difficult to setup for this solution?  We are getting feedback from our application service provider that this is difficult.  I have configured the steps from the user guide, which were not difficult, and I have the DBA's looking at their steps (which is where we're getting out pushback).