First drain the steering fluid. Turn the steering wheel all the way to the left...
...and undo the little screw on the steering box...
Catch the oil as it pours out.
Disconnect the supply and return hoses from the power steering pump.
Disconnect the centre steering stay ball joint from the Pitman arm.
Centre the steering wheel if you wish and then disconnect the rubber flex joint between the steering box and the steering wheel shaft.
Whilst supporting the steering box remove the four bolts that hold it onto the side of the engine bay. The heads for these bolts are in the wheel well. Warning:- the steering box is heavy and awkward – mine weighs 14kg.
If you struggle with these stages, stop and ask yourself if you really want to continue. Adjusting a steering box does get a bit harder than this! (Please note I've given you a bit more information than that presented in
http://www.davidpetryk.net/Mercedes/Steering.htm, but I do agree with the “If you can’t figure how to get the gearbox off the car you don’t need to be taking it apart” comment)
Clean the outside of the steering box if necessary with your favourite engine degreaser.
Remove the Pitman arm.
For removal of the Pitman arm there is a special tool / puller for it – but chatting with the chief mechanic at the dealer he said that you usually have to resort to using heat (and lots of it). I tried with a Butane blow torch but it didn't work – shame of shame I got the mechanic to remove it for me. I don't think he bothered with the special tool.