Arduino

Hay guys,
I just making this thread in order to ask if anyone has any particular experience with arduino, as I have a couple of questions to do with it.
1) how much effort is it to set up an arduino robot?
2) where would be the best place to buy arduino?
3) what is the best place to learn the arduino programming language?
Thanks,
Bertie

By robot, it'd need a Arduino Board, a Motor Shield, an Ultrasonic Senor, 2 Light Sensors, a Compass Sensor, an IR Sensor and at least three motors.

Another question, is there such A thing as a color sensor (a la NXT) for Arduino?