Tamu gave sage advice. May I add that if your dad is considered a good candidate for surgery, another benefit of the robotic surgery is much less blood loss and generally less traumatic to one's innards. I think that this method opens up the surgical option, which I feel is the most likely curative, to older men.
Secondly, when I was diagnosed, I was terrified, but wanted to know as much as I could find out about this to give me as much hope as possible.
Two very good books which I heartily recommend that you get or check out of the library, and discuss with your dad are:
Peter Scardino, M.D.- The Prostate Book, and Patrick Walsh, M.D.-How to Survive Prostate Cancer. Both give similar information, yet there is non-overlapping material. They can help with the decision making, and tell about what to expect before, during, and after all the treatments.
Your dad sounds like a young 70s kind of guy, and if it were me, I'd try for the most curative solution. My dad is a youngish 87, and has a PSA in the 0.somethings, but if he came up with PCa (our shorthand for this condition) I'd try to see if I could get my doc to operate on him with the robot. As you will see from the books, all the options have some downsides.
Sorry you had to come here, but we all are here to help each other. Stay tuned.