I feel your pain. I've gone through replacing the block heater not once, but twice already :S
And yes, first time the dealership didn't have it so I had to drive it across town the next day to drop it off. Second time, different dealership, I talked to the parts department in the morning to confirm they might have one and nope. Had to leave it over night for the next 3, yes 3 days for them to complete it.
Otherwise car is running great :P