You can buy a kit with the boot, bands, and grease. Pull the old one off, put the new one on, pack it with grease and secure it with the bands.

I figure that when the boot dies, the CV joint is probably about to follow. I got a new axle for $80 shipped off ebay, so it wasn't worth my time to replace the boot. You can choose to replace the boot, but it is much easier just to swap the axle out with a new (or remanufactured ) one.