do yourself a favor, do a search on alignment and read the horor stories. I've learnt the hard way as well. Don't waste anymore time and money on these alignment shops. go to the dealer. they charge around a 100 dollars. and get it done correctly. there you wont have to deal with the answers like "this is my first mercedes ever that i aligned".
but then again some think that we're 'pro mercedes dealer' here and therefore will recommend going to the dealer. but from personal experience, this is one thing you should get done at the dealer.
and to my surprise the dealer in NJ did the alignment for 10 bucks less than sears ! and sears is the one who screwed up my front end while trying to re-align a perfectly aligned car to begin with.
they wanted to be proactive. lesson learned: never ever deal with sears unles you're buying tires. even then don't have them balance the tires because their machines are not calliberated ! so have them install the tires and get them balanced at another tire specialty shop.
that's all what sears is good for. tire.. even at that point they end up trying to cheat you out of money. so make sure you shop around for the prices first. they now beat the tirerack prices by addiing the shipping charges to their price. fyi.
good luck and keep us posted.

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Whether you think you can or cannot, Either way you're right!. by Henry Ford.