I'l be changing rotors for a friend of mine tomarrow on a 99 accord coupe. Need to know if I'll have to bust the axle nut open and separate the axle from the hub?

 

A 99 just has screw set rotors. Your going to need some finesse to remove the screws though, they get stuck pretty well. I like to use two ball peen hammers. A smaller one with the peen side on the philips head screw and another larger one to hit the small one. After two good hits the screw should come right out. It's much easier than beating yourself up with an impact driver.