...just one other thing about the chain being longer. You don't want it too long because the rear derailer has to take up the slack, and you already know what happens if your rear derailer is unhappy

[edit] I just found Sheldon Brown's page on chains and rear derailers. I highly recommend you read it then read it again and take it all in. Sheldon is Encyclopaedia Biketannica and his site is the best d.i.y. bicycle maintenance info on the net.

http://sheldonbrown.com/derailer-adjustment.html#chain