Replace the entire stay unless the wire is less than 5 years old. Returning from Tortola 2 weeks ago the stay on my stay sail (6 years old) snapped off just below the swage. Luckily, the halyard kept everything from hitting the deck. The rigging had had a complete inspection in the Fall and the stay had been taken off the boat in Febuary to replace some bearings on the furler. Sometimes you get no warning of failure - you've been warned. Have the rest of the rigging inspected as well.
Another reason why I don't like SS rigging. It usually will last for a very long time, but give little to no warning before it fails.