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A quick diagram for you:
http://xs320.xs.to/xs320/07404/diag.jpg

I wouldnt worry at all about that, it would come into play only if you had a large amount of leds. If I was doing it I'd just wire them all up to a 47ohm resistor on the 5v line

Welcome to the forums, for getting your resistances just put your figures into this calculator: http://led.linear1.org/1led.wiz
It would be better to wire them in paralell (although you wont notice...