When you think of changing your career midlife, the best way to do it is to go to school once again, but it could be the worst also depending on what field you are choosing. When you were in college what you wanted was to go into a University; hence you studied the field that allowed you to go to the University.
Now there is nothing to worry about learning. The only way that you could get confused is on making the choice. With online education in place you have many options to choose from.
In case you need to change and go to a different field you have options to educate yourself even of a MBA online and you cannot gauge if you basic degree has any value now.

