Changing careers at 16 years into a job, is it realistic? - any advice?

After 16 years as a bookkeeper I am thinking about moving into a different field. I have read a lot of threads here and could not find my exact situation. I have good customer skills and I am comfortable with spreadsheets.

I began with informational chats, then a short online course, then a related entry-level role. It took about 10 months.