It's really easy to do!! and with Blinky, EvilBob, HalloweenBob, BucaneerBabe, dudedrummer and a host of other better than Disney Imagineers here you'd never be lacking for help! Just a simple one servo action to swivel the haed back and forth.. you know what they say:
Once you go servo, you'll never let go! well, maybe you dont, 'just made it up