The control arm should not be removed for ball joint replacement, just the spindle.
The ball joint should be pressed into the spindle using the special tool designed to do it. Any machinist will quickly verify this on examination. The head of the tool uses all the area possible to get a straight shot.
I would also only use MB or Lemforder ball joints, as you said they are cheap. They only list for $33.50 from MB.
We press the joints into the spindles for .5 hours a piece or $65 for both sides. We charge 3.3 hours to do the whole job (except alignment) to gauge your savings.
Bosch Master, ASE Master, L1
33 years MB technician