Well, the right way to do it is replace the entire axle shaft. however, if it has just torn, and you would like to not drop more than you need to, you have another option. You can get a "split" boot repair that will let you put a split boot over the old one and seal it together with either lots of little bolts, or seal it with silicon. I actually did this on another vehicle and it lasted fine for 7 more years. They key is making sure there is no/virtually no dirt/grime in the joint, and putting lots of new CV grease on it. Mind you this only works if the joint isn't damaged from being exposed--if you are noticing a popping sound when you turn the wheel hard, this doesn't do anything for you. It's an easy fix to try if you aren't one of those that must have it perfect--and it's cheap (probably $15 total).