Bill Farmer's latest (*The Gospel of Jesus* is the title, I believe, or maybe
*The Gospel According to Jesus*) is a very good introduction to the Griesbach
stance. It is written at a more accessible level than most scholarly work, and
should match the level of students you describe.
Also, Farmer takes his own personal and ecclesiastical locations into account,
a practice we all can benefit from.
Grace and peace,
Perry L. Stepp, Baylor University