I've been told that my violin has a wing crack. Is it important to the health of the violin to repair this?

Yes, the wing crack should be repaired as soon as possible. While it will not degrade the value of your instrument it could prove to be difficult to repair if left for too long. As the seasons change the instrument expands and contracts and the crack may not want to come back together properly. In addition, the longer a crack stays open the more likely it is that dirts and oils will get into the crack and not allow the glue to adhere.