I know it doesn't help being told not to panic because it's a natural reaction to what sounds like horrendous news. But you need to try and put it into perspective.
Prostate Cancer will affect 12% of men however as a cancer, it is one of the most curable, and in cases where it isn't, it's extremely treatable. In fact most men with die WITH prostate cancer, NOT because of it.
The process of testing, biopsies and scans is designed to inform your specialist of what state it is in so that they can recommend the best and most effective treatments.
It may be a combination of drugs and radiotherapy or an operation to remove the prostate completely. I had the latter and panicked beforehand but now, 6 months later, I look back on it as way less eventful than I ever anticipated.
There will be some side effects, some sort of incontinence and erectile disfunction - neither will kill you and both have solutions that can make them less of an issue. Living with them is just something that you (both) just get on with and enjoy the rest of your, very likely, long lives.