With enough determination to do what you want, you can do anything, age is an irrelevancy when there's enough drive to succeed. Leaving customer service will do wonders for your health, I spent 7 years in it myself, I was damn good at it, too, but burn out in that profession is very real. My mental health has improved (not without fluctuation) since I put it behind me and I don't have a hatred for the general public anymore, which I think is a pretty big step forward. As a rule of thumb for leaving any job, though, make sure you have a solid plan in place before you make it final