Changing careers at 12 years into a job, is it realistic? - what worked for you?

After 12 years as an electrician's helper I am thinking about moving into a different field. I worked as an electrician's helper before this. I have good customer skills and I am comfortable with spreadsheets. How did you start?

Thanks for writing this out. I went through something close to it 8 months ago, and it settled down once I kept a simple log of every call and form.