Forty year old guitar player?

I would say you should go for it!! I personally lived a similar situation. As a "youngster" I thought it would be great to be a writer, but my mother believed that that was the most impractical idea on earth and pushed me to study for a real career. So I did, but at the same time I never gave up my dream. My first book was published while I was in my late 40's and now at the age of 53 I am working on my third. Who says you can't teach "an old dog" (cough-cough) new tricks? Definitely not me!