Hello LW and welcome from me too.
It is very hard to be positive when you get that initial diagnosis. Cancer is such a big scary word but it covers a lot of types.
If you go to Publications on this site you can look at/download/or order what is called the Toolkit. These are a set of booklets explaining various treatments, POSSIBLE side effects, emotional reaction etc. I say possible in that way because not all men react to the same treatment in the same way. Some sail through and it's a success, some suffer dreadfully and it's a success. For some it might not be the treatment for them, in which case it can be tweaked or perhaps dad might be offered a Trial.
The Toolkit will eventually be useful to help you ask the questions you want answers to.
As a worrier this situation is made worse for you but try not to let it exhaust you. In the weeks and months ahead you'll be there for both your parents. Just do what you can, when you can and I'm sure they'll appreciate you even more for it.#