I know you have plenty of friends, but this is one of a different nature. If you own a car that is out of warranty, you have to establish a relationship with a fair, honest, competent, and efficient independent repair facility. That being said, finding one my be a tough task.
There are several ways to find a repair facility. Asking other Mercedes-Benz owners is one source, and online reviews is another (though not always reliable). But sometimes you just have to resort to trial and error. You will want to look for a tech or service writer who will communicate with you, giving you a fair estimate of repairs, and completing the repairs close to these estimates.
If you find such a facility, love, cherish, and let them know how much you appreciate the business, because they truly are a dying breed.
Ken