It requires some change of diet, but honestly when you get down to it, it's not too tough. Sounds like you have a very good start thus far. He should be recording his blood levels to monitor how different foods are affecting the levels. Did the doctor provide any specifications on that?
I'm not diabetic, but a few years ago I was diagnosed with hypoglycemia- pretty much pre-diabetic. I have to regulate my blood sugar levels, which run low, otherwise I could have the adverse affect and end up diabetic. I spent some time with a nutritionist and also recorded my blood levels every 2 hours or so. It was tedious at first, but after awhile you will soon figure out how to keep the blood regulated. Good luck!