Control arm replacment
 

When I replace lower control arm on a 124 chassi do I have to mark something up or just take it apart the eccentric bolt and change the control arm.
When I tighten the eccentric bolt the car need to stand on it's wheel do I tighten to a specific torque or do I adjust the camber with the eccentric bolt torque.

Take the old arm off, and install the new arm. Tighten everything when it is on the alignment rack.

Don't tighten the eccentrics until the suspension is fully loaded, or else you'll damage the rubber bushings. Do a search - there is plenty of discussion of W124 control arm replacement here.