Prayers for Dad and for you. Been there (my Dad). It’s a long surgery and long recovery; I am hoping right along with you that they have caught in time for him to finish spending your inheritance (LOL!) God Bless.
First my prayer is that G_D will guide the surgeon's hand and your Dad will be blessed and survive to spend many more years with you and your family.
Yes, it is a very complicated and long surgery. It will take a while to recover. A lot of nerves and organs get removed or reconstructed. Life will never be normal again but he can live with the outcome if the cancer is eradicated. Trust me, it is worth it.
In October 2002, I had to make the same choices as your Dad. Time is very important as the cancer spreads very quickly. Usually by the time one is diagnosed the cancer is inoperable and many times survival time is measured in days and months. It is a good sign that your Dad has qualified for the surgery. Many don't qualify because the cancer has been found in a later stage. Mine was detected at an early stage. Even so, I was obese (370 lbs) and in my late 50's. I was weak and not very healthy.
By Thanksgiving day I was in surgery for 9 hours undergoing the Whipple procedure. Everything went well and I was expected to recover. But four days later I was back into surgery for another 9 hours because my body was rejecting half the pancreas and spleen that they tried to save and I was running a 104 temperature from infection and starting to deteriorate fast. They removed the rejected pancreas and spleen and cleaned up the infection and off I went into intensive care and an induced coma for 14 days. When I finally awoke from the coma, I was very weak and had to relearn to walk, function as a type 1 (really type 0) diabetic, eat differently, and cope with many other life style changes. The prognosis was I had 2 to 5 more years at best.
To make a long story short, I don't know why I'm here except to say to others who are walking this path, that there is hope and not to give up. I honestly believe it was my faith in G_D (the father, the son, and the holy ghost) and the prayers of my family and many friends (of all religions) that saw me through this crisis. And they will see your Dad through his. Remember it's in G_D's hands whatever we face. May G_D bless your dad, the surgeon, the medical staff, you, and your family and friends at this time. And be brave...