So sorry to hear of your dads plight . I was dx with PD in June 2014 I'd been to gp with problems for 2 years prior to dx but told I was not young anymore and i was working to hard!
It wasn't until I collapsed at work including a total cognitive melt down that I was seen by a nuro who dx PD after a 20 min examination saying I likely had it for 5 years prior to that.
Im a mechanic / engeneer and have had to give up my work due to PD as trying to do fine detail work with shaking hands and a poor memory is not good,
Just being there for your mum n dad is the most important thing and finding out all you can about PD and the help they can get. You will find loads of info here and people who will always listen and advises where they can, and there's no better place to vent your frustrason as we all have same problems and needs.
So my best to you and your mum n dad
Live well Cc