I'm in a similar boat... after a 10 year IT career that has been profitable but ultimately unfulfilling, I decided to pursue my original dream of being a physician. Mind you, at the time I was 27 and had one less-than stellar year of college under my belt, so I was starting from scratch. I enrolled at my local state school and two years later I'm still grinding my way through an undergrad degree + pre-med requirements. If all goes well, I hope to enter med school when I'm about 32, which puts my final completion date at around 40 years old. (With about $200K in student loan debt, most likely. )

And you know what, in 10 years I'll be 40 years old anyways. I might as well be doing something I love.