I don't think you can just get a new ball joint and press it in.So I was working on the car and noticed the little ball joints in the rear wishbones are blown. are these replaceable or do I have to replace the whole arm?
where is the best place to order these parts?
Get hte the whole arm, as you will also get the bush at the other end.
They are a common failure, along with the ball joint (not a normal looking balljoint) within the wheel carrier itself.
Rear Wishbone costs about £180 or so, per arm. So from my experience that sort of works out as $180 - $200.
Go for BMW dealer or Lemforder only , I would say.