upper ball joint isnt replaceable. you shoud be able to replace the boot however, maybe, with a boot from your stock arms...(not sure tho). or from a dealership.
lower joint, try an open end wrench that fits snuggly around it and pry, while tapping (sometimes means beating the piss out of) it with a hammer or mallet, preferably one with a lifetime replacement warranty.
dont forget to repack them good with grease.
EDIT:above post about replacing the upper ball joints, interesting info. i would think it would have too be cut out and then a ball joint with snap rings or something would be the replacement...