Re: belt wrap question
Dude!
I don't know about the SLK but on the SRT taking the fan out of the car (thus out of yer way) takes all of one minute. That would give ya extra clearance to work.
Not sure which torx you are talking about. The tensioner?
On my cars I use a 15mm box wrench and use the nut that is also on the tensioner to release the tension. Don't yank on it as you will loosen the bolt. Just apply smooth pressure and the tensioner will pull back.
Let me know if this works for ya.