Well, I live in San Antonio and work in Austin, so I know a little about both...so assuming you're like me and would rather let someone else get covered in grease (at least for this job):
In Austin:
I typically use Ben's Workshop--they are at 410 Pressler St., 512/472-5555; I think lately they've been telling folks that they aren't taking pre-1990 models that they haven't previously serviced (wish I could afford to be that picky in my business...) but Ben is a very kind fellow, works only on MB, and if it's obvious you care for the car, you could probably get him to do it. I've always had good luck w/ the shop--it's super clean and everyone is quite nice. Labor was $75/hour when I was there in June of last year.
I have also used Phoenix Motor Works at 1217 W. 6th, 512/474-2072 when servicing the diesel Volvo (they are one of two places in town that'll even look at the thing). They also do good work--but they are not MB specific. Labor was around $80/hour in January of this year.
In San Antonio:
I typically use Kehl Motor Service at 10639 Nacogdoches Rd., 210/655-6140. They are by appointment only. Interesting folks who have always done a good job for me, but I typically get the car serviced in Austin, so I've only used them a few times. I think labor is about $75/hour; it could be more.
I have also used Autobahn Automotive at 2306 NE Loop 410, 210/657-1180; they aren't MB specific but they do good work and are very friendly--the morning service writer there is named Tommy, is a super nice guy, and will work on the Volvo, which makes him a good guy in my book--they have done an excellent job working on that car, the only thing they've done for the MB was replacing the P/S pump.
Anyway, those are my suggestions--I hope others will chime in and I hope you know that this response is based on my experience only--I'd hate to be "that guy who told me to go to this crappy place, etc."
Good luck,
Chris