What size is the nut holding the steering wheel on? I only have metric sockets up to 22 mm in 3/8" and 1/2" drive, I would buy a bigger set but I have only Snapon hand tools, stuff, so it gets expensive when you go that big. Call me dumb for being brand loyal haha...

Ian, I'm sure Snap-On likes you're loyalty but unless you work professionally I think it's unnecessary to spend so much money on tools. You can get by very well with Craftsmans for hobby wrenching. You can easily buy three or four wrenches or sockets for the price of a single Snap-On. It's also a PITA to get a Snap-On replaced unless you have a dealer regularly visit you where you work.
Think of the money you can save. You can buy more Mercedes stuff.;)
Just my 2¢.

Haha yes, but remember, I am a machine shop owner so I need the best quality and have the snapon man there ever week, so im taken care of. I am of the mind you get what you pay for so I use Starrett or Etalon Precision tools (machinist's tools) and Snapon handtools. Just MY $0.02 haha

Regarding the bolt in the steering wheel, it's just a 10 or 12mm hex key socket.