You can replace just the boots, but the common wisdom seems to be to just replace the entire shaft (especially if you're considering DIY). You get fresh assemblies, seals, and boots - and the removal/install process is a fraction of what it takes to replace a boot. Not too much extra expense, either. See
here.
If you want to try replacing the boot yourself, see
here. -How long has it been torn, and is there still grease in the CV joint (and no grime/grit in it)? If the joint is worn, you'd do better getting a fresh shaft as well.
I'm pretty sure the repair is different on 2wd - they don't have any CV boots (or CV joints) to worry about, so no repair needed!