No, you do not need to re-do the assignments unless you want to try to hear a higher coursework score. Keep in mind that the coursework is worth 30% of the final grade, and the proctored exam is worth 70%. (If you do repeat the coursework, but your previous coursework score is higher, you may carry this score over to that particular term).
If you plan to only retake the exam, you will need to enroll, upgrade, and request to carry over your previously earned coursework score by submitting a form that will be sent via the in-course emails before the proctored exam period.