Just diagnosed with Neuroendocrine carcinoma

My Dad turns 90 years old next month. He still works 6 days a week at the retirement center. He has never been sick with anything. Not even a cold. As far as my brother and I can remember, he never stayed home from work because of any "sickness" reason. Much to our surprise, he has just been diagnosed with nueroendocrine Carcinoma.
A few weeks ago, following a minor fall leaving on small scratches, a knot began to appear behind and under Dad's left ear. A visit to the doctor resulted in the recommendation of having it removed and tested. Dad, since there was no discomfort, reluctantly agreed. They removed the knot and some lympth nodes. The results were devastating. We have been told it is an aggresive form of cancer. Doing some research on line seems to bear this out. We have an appointment next week to visit with an oncologist who is supposed to assess Dad's condition and make recommendations for the future.
Dad is very confident with his belief in where he will go following his bodily death. We will certainly miss him here but are confident we will reunite with him one day. Our main concern is the process between here and then. Does anyone have any words of wisdom on how to make the process as pain free as possible? My brother, my wife and I understand everyone is different and what works for one, may not work for another. However, we are new to this cancer/teatment arena and would appreciate knowing if anyone can speak from experience about making the transition as painless as possible.