My LBS sells bearings for $.04 each. <$2 of bearings should cover it.
It couldn't hurt.
I also look at the races under a 30x jeweler's loupe. If I can see any pitting or brinelling I toss them and get a new headset. Headsets online are pretty cheap. For $20 you can get a pretty darn nice one. For $5-6 you can get a basic one. Why mess around with worn-out carp?