I've changed a ball joint on Taynar's car after the rubber boot was damaged during the strut install.
Ball joints are not difficult to change, but they do involve removing the strut on the side you're changing. They are held in with rivets, I removed the rivets by drilling the heads off and then drilling a pilot hole through the shank and then pushing the rest of the shank out with a pneumatic hammer. New ball joints come with a new boot and are held in place with bolts rather than rivets becasue 90% or more of auto shops do not have the proper tooling to properly install rivets.
depending on what kind of lower A arms your car has it might be more cost effective to just replace the entire control arm. There are two kinds, one installed to the sub-frame with spherical bushings and vertically oriented hardware and another with cylindrical bushings and a horizontal shaft attaching them to the frame. I'm not sure which but one type is considerably less expensive than the other.
