i just replaced my ball joints yesterday. i bought them individually (just the ball joints, not the whole lower control arm) from a guy on 3si. user CustomShiftBoot sells ball joints for our cars for $99 shipped for a pair.
here is one of his many threads. he had a sale over the summer, but still, $99 shipped for a pair is a very good deal. they are OE quality ball joints, so don't think by the price that they are crappy knock-offs.
as for removal/installation,
this thread has many pictures and describes in detail how to do it. its actually pretty easy, and you only need 2 special tools (pickle fork & ball joint remover/installer kit) that you can rent at your local auto parts store.