Welcome to Pet Talk.
Sorry to hear about you GSD.

I could not find much info. about Pancreatic Insufficiency
in my vet book.

Just that a lack of enzymes causes incomplete digestion of foods in the small bowel and a malabsorption syndrome.
(did mention it was prevelent in young GSD)

Treatment: Most important is to Feed a highly digestible diet.
Simultaneously, the missing enzymes are given by mouth,
using a antiacid or acid inhibitor is usefull, Fat-soluble vitamins should be supplemented. It states in most cases lifetime
treatment is required.

I agree, it does not hurt to get a 2nd opinion.