First, let me applaud your question--too many folks wait until after they've invested the time and energy before deciding that this is the path they desire.
My thoughts (which, along with 35 cents, will get you a cup of coffee at our local canteen) are as follows:
1. Decide on your goal. As my colleagues have indicated, this could include money, an 8:5 job, research, whatever. You need the goal to decide the path. Any monkey can make a lot of money selling stocks or insurance (no offense intended to any monkeys who might be reading this!), but that will not lead to happiness. For me, the goal was to have interesting work every day.
2. Don't feel that you won't be able to 'change direction' if you find yourself on the wrong path--better to restart than to continue down a path you don't enjoy. The good news is that your downside risk is pretty small on this path--the degree is pretty flexible and the income is pretty reasonable so that changing jobs or returning to school are both quite possible down the road.
3. It's pretty cool to be able to explain things to my three year old daughter when she asks her barrage of 'why?' questions.
For whatever it's worth. And best of luck to you.