I've been pretty pleased with German Car Service, 801-264-9911, 4325 S. 300 West, just off the 45th south exit of the 15. It was the successor to Werner's, which was the most prominent SLC indy for many years. After Werner sold his shop, he got tired of retirement and started this one up. He's passed away, but his son Mel runs it now. $65/hour shop rate, they do good work. I've had my SD in there for a few things, no complaints.

Werner's is also probably fine, but I have no personal experience there. www.wernersmercedes.com.