Sharing my dad's experience.
Dad is T2.
He had Whipple procedure just this March. Pre-malignant tumor in the pancreas. We are very lucky that it was found before it turned fully malignant (thanks to gallbladder stone pains too, of all things, lol)
Surgery took 7hrs, 5days in the ICU, then 2wks in a regular room because somehow there was still blood in his stomach after iirc 5days, and when he was instructed to get an ultrasound of the abdomen, he had to drink water, and he had to... err... puke everything out right after ultrasound, and what came out was black liquid in larger quantity than the water he had drank. We did get scared, but all trouble was over after that.
After all that, went home, home rest for a week. The next week, tried to go to office but got tired too quickly so we went home early. It maybe took 2months for things to *look and act* normal, though I did have to clean out his JP hole and the surgery cut everyday for at least a month.
All in all I'd say it took 4months for him to be almost-completely normal, but until now he complains of a feeling of weakened legs.
We had to visit our endo every month until July, to adjust his insulin and oral meds. The first 2 months it felt like he had absolutely no diabetes lol. Everything was normal and the endo even removed his insulin, and reduced his meds intake from 3/day to 2/day at lower dosage. But currently, his BG has been up and down. I'm not sure if it's still post-op symptom or lifestyle/meal change. From what I read about T3c, it seems he could be affected, if his BG continues to be uncontrollable...