I found a list of approved ATF fluids/oils that meet our transmission manufacturer's approval.
For others who are looking to execute this DIY, this is not a Mercedes gearbox like in the 996. This is a ZF gearbox and you can find the approved lubricant list here:
http://www01apps.zf.com/kst464/ZF_InteroeleV2_manager/Work/2012-04-01/TE-ML%2011_en0700.pdf
The very last fluid "ZF LifeGuard5" is what I believe to be the factory fill. It is available pretty reasonably here:
Transmission Fluid ZF LifeGuard 5 - Case of 6 x 1L Container