There are plenty of threads on this - it's difficult. Search around. I almost gave up on my sedan, but finally just put some protective tape around the thing and did it with a screwdriver. No probs.
Current: '11 SpaceGrey 328i XDrive
Gone: '07 SilverGrey M Coupe || '08 SparkG M3 || '01 LSB M3 || '01 TiAg 330ci