My mechanic in Newport is Strasse Automotive at 629 Ohms Way. They're actually on the Costa Mesa side of the border -- near Hoag Hospital. It's a small shop with 3 mechanics including the owner, Stan, who's a former racer.
I've used them on a Porsche, 2 Audis and 2 MBs for nearly 30 years. They're not magicians and don't always get everything right the first time (tough diagnoses sometimes take a few tries). But they're as stubborn as I am, stand behind the work, and usually come through. Unfortunately, Stan's just had a change in personnel on both other mechanics, including the one who works on MBs. So I'm watching the new guy carefully. I've had my diesel in there once under the new mechanic and it's too soon to know if he's up to Stan's standards. As Paul suggested, I've been known to print notes from this forum and bring them in. We'll see how the the new guy deals with that! This will happen first week in April. I'll keep you posted.