This is how I replaced the warn ball joints on my 2000 Pontiac Grand Prix GTP. This should be similar for Buick Regals from 1997-2003, Grand Prix from 1997-2008, and Chevy Monte Carlos from 2000-2007.
I originally intended to grind down the rivets holding the ball joint to the control arm and use a punch to punch them out. That did not work as they would not move at all. I used a 1/8" drill bit to drill a pilot hole and then a 7/16" bit to drill out the rivet. I had to open the control arm hole up to 1/2" as the new bolts wouldn't fit the 7/16" hole.