That sounds more like a caliper on the passenger side. Perhaps the rotor got some grease on them and the pads arent gripping. Causing the drivers side to "bite" more than the passenger, hence the pulling to the left. Perhaps it would pull all the time if they messed with the tie rod and drag link while removing the swivel housing. But, pulling to one side while breaking leads me to think the problem is with the brakes on the opposite side. I would take the wheel off and spray down the caliper with brake cleaner. Couldnt hurt to take the caliper off and spray the pads either. Better yet, take it back to the dealer and have them fix it. But, they will probably tell you the caliper is shot and want $3,200 to repair.