I did this install with friends in my garage. I had the car on jackstands and it was a little bit of a pain. I think $1100 is a steep price. Once I loosened the diff, I just moved it back a few inches and had a friend swap the bolt and rear trailing arm.
MODS: 03 M3, 6MT, PSS9, AFE Intake, El Diablo Exhaust, Turner Motorsports Rear Adjustable Camber Arms, PowerFlex bushings, 18'x9' square setup & one driver that grins ear to ear everytime he is driving it