The most important thing to cover in an Ambassador training is what the expectations you have for them are. Because Ambassadors are the first point of contact for both instructors and students, it's important for them to know what your expectations are for what they will do, what the instructor will do, and what students will do. If the Ambassadors aren't interested in a particular facet of the role description you've created, then you'll need to find additional support for the classes that particular Ambassador is supporting. Having clear expectations up-front for all participants will make your pilot go more smooth.
Campus Ambassadors who are not experienced Wikipedia editors will need an overview of core Wikipedia policies and the basics of editing. All Ambassadors will need an orientation to how you anticipate instructors using Wikipedia as a teaching tool in the classroom, as very few of them will have information on best practices in assignment design.
If you're in one city, it might be worthwhile to do an in-person Ambassador training for your first term of your pilot. Bringing Ambassadors together establishes a group camaraderie that can be useful in helping resolve challenges as the term goes on. But these in-person trainings can get costly quickly; you might also want to translate the on-wiki Ambassador training into your language to send Ambassadors through on their own time.