Hi there,
The lower ball joints are pressed into the control arms, the top joints are riveted. The factory manual recommends against replacing the upper joints due to the problems of re-riveting, but I have read that people have bolted them in with no problems. The lower ones require a press. - a 10 ton Harbor Freight style should work fine. If you are going to the point of removing the upper and lower control arms you should replace all the bushings also. You might check out the prices on brand new replacement control arms, they already have new bushings and ball joints installed, and if you price it all out, they aren't charging TOO excessively for the arms and labor. They are available from several sources on the net.
Also, be sure to check the subframe for cracks in the metal around the lower control arm mounting tabs. I just replaced the subframe on my '82 as the rear tabs on the left side broke clear off!

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C