The ball joint part is less than $40. It looks like no pressing is
needed. Therefore, I would say no more than $100 (one side) at
independent. However, wheel alignment is needed after replacing the
ball joint. That is another $100.
My guestimation is based on my own experience (at rate around Washington
DC, USA), not by standard method (there is labor hour reference for all
works, for all cars). However, I don't have experience on your
particular model so the figures may be off (but should not be too much).
I did 01 E320 radiator myself... it is not too hard to change yourself...
you got tons of room to work on it. The only thing was a pain to get to was
the transmission oil lines...
Don't forget radiator hoses too.
As for lower ball joint, alot of time, they rather change out the lower
control arm instead of the ball joint itself so that is why it is so
expensive. But it is not like they got to take a bunch of stuff off... I
think they just have to pull the lower ball joint off and two bolts to get
the arm off... Everything else hangs on the strut.
I'd say if you can find one to replace just the ball joint... $200 here...