So much will depend on how bad the damage is. If he still has a partially functioning pancreas there is a chance he may be able to get off the meds if he is very strict.
There are a number of small studies out there showing the benefits of low-carb eating.
A low-carbohydrate, ketogenic diet to treat type 2 diabetes
Effect of a high-protein, low-carbohydrate diet on ... [Diabetes. 2004] - PubMed - NCBI
Effect of a low-carbohydrate diet on appetite... [Ann Intern Med. 2005] - PubMed - NCBI
what looks like a good resource
Effective Diabetes Treatment
Eating primal is not a diet, it is a way of life.
Don't forget to play!