Do you need to break the chain to put the wheel back on no. Just put the chain around the cogs and slight the wheel on..

Check out partools and sheldown brown's web site they have great how to's on repairing bikes.. would be first thing I would suggest. THe headset just check under threadless headset. THe stem screws into the fork that is what that top bolt is for. There is a large nut that you can screw down to tighten the headset.