1) Yes, you need a resistor. You choose the resistor value so that you draw 1A. For instance, if my LED drops 0.7V and my supply is 12V, then I have 11.3V. I want 1A, so I choose an 11.3 Ohm resistor (Granted, 11.3 is hard to find :-P So either make it in series/parrellel or use a slightly larger one that does exist)
2) XBEE is UART, if I'm not mistaken. RX -> TX, TX->RX, make sure you tie the GNDs together and keep the voltage the same. IF you want to use USART (the S stands for Synchronous), then you get to use the clock stuff and CTS/RTS.