Rick,
The only recommendations I can make are to:
Familiarize yourself with the ITIL framework for ITSM (I think they cal it SO now). Almost every commercial or open source package is written with that as the foundation. However, be aware that you are not going to learn enough to "knock it out of the park" during your interview. ITSM is a bear to learn and process. But, at least try to get to get some knowledge of the service lifecycle. The pdf in the link below should help with the lifecycle and all of it components. Whatever you do, if you don't know the answer to a question, don't make one up. In my experience, Germans are sticklers for the details especially ITSM.
http://itsm.zone/samples/PPO.pdf
Second, familiarize yourself with CMDBs and their jargon. A good CMDB, and a good CMDB update/maintenance policy are key for making ITSM work