Broke a spoke riding today. It was cold 31 degrees, the road was realatively smooth, flat and straight at the time. It was a rear spoke and the bike is about 1 year old with about 2k miles. I stopped imediately and called for a ride home. My questions are:

1. Should I replace the broken spoke or should I assume that there has been uneven stress caused by the failure and replace all the spokes in order to avoid a chain reaction of additional failures due to the stress created?

2. Since spokes get stress and progress toward fatigue with each revolution shoud I replace the spokes in both wheels.

3. The wheels are Shimano RS-80 with stock spokes, should I replace the spokes with a lighter better spoke?