Hi geggie and welcome
Ya know, that is a fabulous question as many don't know which approach to take. Bruce has many wonderful notations/suggestions and a terrific start.
I know, for me, I met with my primary care physician (in network), she made the surgeon recommendation, in which I called my insurance provider, and they confirmed the dr and location of possible treatment was covered on our plan. So, knowing financial weight was off my shoulder from the onset helped me to keep in focus for discussion treatment options.
Yet, Bruce is right as well. Finding out the most qualified person to treat your dad's AN, taking into consideration your dad's location, plan of treatment, etc, all need to be taken into consideration. Some may say "heck, just get in great hands and we'll deal with the money issue later, as the health is the priority".
Going to sit back with my virtual martini to see other others chime in as well... great topic. I'm sorry you and your dad are going through this journey, but know we are all here for you and hope you find answers, comfort, friendships and yes, a bad drink or joke on occassion, to help you.
Again, welcome!
Phyl