cv axle

my car needs new cv axles, and im planning on changing them myself. i have no mechanical experience, but always wanted to learn and figured i might as well learn on my own car. is it hard to change on a sentra? im planning on just buying and following a chiltons manual, but if i screw up could i be in a life threatening situation? i dont even really knwo what the cv axle does, and whats the difference between it and a tire rod? complete newb so any advice will be welcomed. thanx