Everyone's Parkisonson story is unique but when I was first dx'd I was really freaked out and thought my life was over in a manner of speaking. The reality a couple of years after the first dx (which I did not actually believe until more recently, getting a second confirming opinion) is it has been very manageable for me and I am very optimisitc that it will be years before the disease really affects me in any subtantially limiting way (I am in my late 40s). I do have to take meds and some days are better than others but only a handful of people even know my dx (and only because I chose to tell them). In fact some of those I have told seem to suspect I may not really have the disease. I am able to work a job that involves a great deal of responsibility, travel, have fun and live a normal life, other than knowing I have this disease.
So my point is, try not to react too stongly even though it is a very scary diagnosis. A good doctor can do great things and it may be years before your father has any symptoms that really impact his ability to live normally.
As far as where to start, you are right, knowledge is power. I have found the best concentrated source of info. is the Michael J. Fox Foundation site. There is also a "Parkinson's Disease for Dummies" book that is pretty good. This website is good too although keep in mind the disease varies a great deal by patient so you have to be guarded about drawing conclusions form other people's experiences.
I hope that helps. Good luck and God bless.