If it is only the bearing and the seal that are bad you can replace those. If you are mechanically inclined enough to get the box out and back in they you can change the seal and bearings also. The money is in getting the box out. Once the box is out you could take it to MB and get them to do it. They are going to charge you $200 by the time it is over but they should be able to adjust the box properly.

Also chek the coupling between the steering shaft that comes out of the car into the engine compartment and the box. You can turn the wheel slightly and watch the shaft to see if there is slack in the coupling.