Find another alignment shop that knows how to do a M.B.
There is a plug on the bottom of the steering sector that gets pulled, then as the wheel is turned you can feel a dimple with a small phillips where it is centered, if they have the equipment and know how to do a M.B. they will have a tool that screws in to hold it centered. They also need a spreader bar to set tow. This is spelled out in the manuel, also their machine should tell them they need special tools, also ride height needs to be checked at the rear or caster could be off. Take it to the dealer.