My mom was just released from a SNF. Seeing her neurologist soon, Parkinson’s. Should I ask him to explain the progression of disease?

I think one of your paragraphs says it all. There IS no certainty as to what an individual's progression will be with this disease. Some do very, very well for a very long time, and adjust around the symptoms. As with things like MS it is very individual. I love the one who listed the "For Dummies" book, as I love those books for just about every subject on earth. I think that the doctor will tell her that it is a day a time sort of thing. As my Dad's doctor said to my father when he was diagnosed with cancer of the prostate in his late 80s "This is very unlikely to be the thing that kills you". He was right. My Dad went well into his 90s, and it wasn't prostate cancer that caught up with him. So it is just "a day at a time". There are many out there now publicly dealing with Parkinson's disease. Wishing you both the very best. PS, remember also we are all different. I like personally to read everything, scare myself to death, plan my funeral, then move on. Things I don't face dead on keep coming at me in the night.

The book: Parkinson's for Dummies was very helpful, and not too scary.
I believe it was written by specialists from UCLA at the movement disorders clinic.

Knowledge can actually decrease fear and allow you to be better prepared for all possibilities, some of which never happen.

Knowledge can help you accurately report changes to the doctor so meds or treatment can be adjusted, which may happen frequently in some. Keep in mind, that some patients rally, just when we imagine the worst. This can even happen in the course of a day.

Not every Parkinson's patient is the same, not all experience the same symptoms and not all progress at the same rate.