front right lower control arm ball joint replacement?

my 2000 lesabre's right lower control arm ball joint is damaged...

i was told by a mechanic the entire 'arm' needs replacement as the larger ball joint can't be replaced? is that true?

thanx

Yes., by oe design. Also what is damaged, a ball jount wears out.

Yes., by oe design. Also what is damaged, a ball jount wears out.
i was told it was the ball joint....

and since i've posted earlier i've found a ball joint at a dealer...or the entire arm from a 'yard'....90 vs 125 dollars....

so i'm going to the dealer to have the ball joint installed..if they say it's more i'm getting the 'yard' arm..for 125...the dealer wants $770 for the complete arm...