All I did was raise the control arm by placing a jack underneath the lower ball joint. Once I had the control arm lifted and thus the spring compressed, I put a 1" threaded rod up through the center of the spring and place one 3/8th's plate on the spring's upper "seat" and place one 3/8th's plate on the underside of the control arm and then place the washers and nuts on threaded rod and "viola"... the spring is kept compressed while I remove the strut, steering knuckle, and ball joint.

From what I could see, once you remove the strut from the sterring knuckle the whole thing could fly apart without having the spring "in check". The control arm doesn't have to come off to R/R the ball joint but it does need to be "steady" so you can press(technical term for beat the ball joint out with a hammer) and then press(with the correct tools this time) the new ball joint in.
That's the way I saw it anyway. Of course I always go around the world to get to the corner drug store.

Kevin