That's very impressive of both your service and desire to attend school once you return. For one, you aren't alone when it comes to being scared and uncertain because you will be returning to school at a later age than most. However, especially in this day in age, more and more adults (>25 years old) are deciding to do this. I can almost guarantee you won't be the youngest one there. The easiest way to figure out the demographics is to just call the school, ask for information, and any advice/information the school can provide for those entering in similar situations such as yours.