Yes. It is only courteous to do so. It saves on paper, time, and effort for the admissions staff. Besides, it gives opportunities for those who have yet to receive a secondary. Congrats on your acceptance to your top choice.
You should, but you are not required to. If you don't they may look down upon future applicants from your school. In addition, if you are offered an interview and don't turn it down, they can just send you a nice rejection letter; happened to my roomate with CCOM.