Changing careers at 15 years into a job, is it realistic? (update)

After 15 years as an insurance claims processor I am thinking about moving into a different field. I would rather hear the honest version than the polite one. I have a little time and a small budget for training. Has anyone made a similar move?

Thanks for writing this out. I went through something close to it 6 months ago, and it settled down once I kept a simple log of every call and form.