Usually if your rub your finger along his gums, you'll feel little nubs where a tooth will be coming through soon. Teeth is a miserable time for all parties involved. have fun.
There haven't been any problems with sleeping. When the teeth first started to come in, I think she was crabby during the day. Her whole sleep schedule is thrown off because of daycare though. I pick her up at daycare where she refuses to nap for 9 hours, feed her, and she's sleeping by 6:30 until the next morning.