Any gateway will work. They just called me and it sounds like they will have a technical person on their side call me to work on it with me directly.
Just finish your site and get it all set up with authorize.net. Then in the support session I can work with them to update authorize.net to the new gateway.
Once you have your site all set up with the authorize.net gateway, request a premier ticket and I'll call you and verify you are at a good point and take payment. Then we can schedule the meeting with their tech to finish.