Yeah, voice control is tricky. The best way I can think of doing it would be to program a smartphone or netbook to do the voice recognition, and then send control signals to motor drivers, etc.
Start simple - the $50 robot tutorial is a must for beginners. I'm 16 and this is the robot I made to get started: http://waterpigs.co.uk/electronics/weave/
It took ages, loads of research, help and debugging, as well as several years worth of messing around with electronics! But the tutorial mentioned above will get you started much more quickly.