Removal of steering wheel.
1. Use a small flat bladed screw driver and gently lift out centre MB plastic emblem. Be gentle and avoid slips and scratches of emblem and butchering of rubber around emblem, it will pop out!
2. Wheel should be mounted with a 10mm recessed nut. Insert 10mm Allen key (one with a T Handle makes it easier). Give it a couple of sharp taps with a small hammer to free the hex bolt. You will need a helper to hold the steering wheel to stop it turning. ENSURE THE STEERING LOCK IS OFF BEFORE ATTEMPTING TO UNDO NUT. Do not use the steering lock to hold the steering wheel in place. If you don't you will probably destroy the steering lock!
Using a long ring spanner over the end of the T handle or normal allen key/ring spanner, it decreases effort to crack the allen bolt (they tend to freeze and make a snap sound when they release). Turn anti-clockwise, loosen, the wheel should then be noticeably loose on the column. If not, loosen,, but do not remove the hex nut and jiggle and pull the wheel by hand, that will free it from the splines. (The nut stops the top of the wheel breaking your nose when it suddendly pops off!. Easy removal, reverse to replace, ensure it's tight on replacement and you have your wheels pointing straight ahead, small amount of locktire on the hex nut's not bad insurance. My two cents.