I replaced my front two upper control arms and was wondering how do you check the lower ball joint to see if it's wore out. Anyone done this and have suggestions on how to check it?

Take a large flat blade screwdriver or prybar and pry up and down between the balljoint and the lower control arm to check for movement... there should be no play (movement) between the balljoint and control arm. If there is you should replace them. Also make sure there are no tears or rips in the balljoint boots.