We just got the Apps-Apex integration working on R12.
Yes you need a separate Apache server, but the rest is almost the same. Nothing has to be changed within the Apex application, you still set the VPD call to initialize the apps session.
Only the menu function to launch Apex from is changed from a plsql based one, into a jsp menu function. So yes, an extra jsp page needs to be compiled on the Apps j2ee server.