1. Extract the XDG3 ISO using exiso v2.7. This will extract the all the files and folders out of the ISO. You can stop here and FTP the files and folders to your 360 and use XEXMenu or FSD to launch the game, or continue to make a GOD package.
2. Use CreateISOGood (by Frogy_007) to create an ISO from the files and folders you have just extracted. This will create an ISO that is compatible with ISO2GOD.
3. Create a GOD package using ISO2GOD
4. FTP to your 360 and enjoy
As always if you require any assistance please visit our forums here and start a new message/thread.