Do you mean the spare? or one of the actaull rear wheels? They are really easy just undo the nuts...lol
You put a jack under the car... jack it up... use a wrench to undo the bolts.... take em out... lift off wheel... voilah... lol.
The same way you take the wheel off of any other car. Not like there's anything special about it just 'cause it's german.
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