As its from a Mercedes dealer and its an approved (and I therefore presume fully guaranteed) car, then you have no worries. If anything goes wrong simply take it back for a full and free fix.
Personally, I love the shape of the CLS and in its AMG guise will go like stink. Trouble is the fuel tank will empty a bit quicker than what you are currently driving (C200K ?).
And your insurance company will be rubbing their hands.
I would love one of these, but I know my limitations - both financially and driving skills wise. So will not be joining you.
Once out of warranty, I do know all AMG's are horrifically expensive to fix, so be aware that your service bills can often be 4 figures.
But on the upside, the enjoyment you can extract from driving such a beast can more than outweight anything else.
I am more than a tad envious.
BTW.....what colour is it?
Black suits the CLS very well - and with that AMG badge on the back sets it off a treat.
Personally, if I was going for a CLS I would be very tempted to consider a 320. Still goes well enough but doesn't empty your pocket nearly as quickly.