Let see...
Statement 1: Your GMAT Score is 690
Statement 2: The Schools GMAT Average is 620
A. Statement(1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.
B. Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.
C. Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.
D. EITHER statement BY ITSELF is sufficient to answer the question.
E. Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question and more data pertaining to the problem is required.
Ok seriously - jokes aside, no, don't retake. There are two reasons for this. First, a 690 to a local school is going to be very high, so you'll be fine. Second, a 690 to a local school is going to be very high, so you'll be fine.
PRO TIP: 690 > 620