I really love all the aerobic classes that they offer at my gym. Can I get my body in shape and my muscles toned by doing those classes?

Unfortunately not. It's important to understand that if you only do aerobic classes, while it will improve your cardiovascular health, and possibly even give you some weight loss, it won't help you develop toned muscles that give you the shape to your body that you're looking for. If you enjoy the classes, feel free to do them as long as you incorporate the high intensity interval principles either separate from the class using weights or prior to the class. One word of caution, be sure not to overexert yourself to the point that you begin losing the muscle you're trying to build.