RepairPal Certified shops can diagnose and repair your 2007 BMW 550i. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
I know this is a post from last year, but I just had mine quoted at a local reputable shop. $3,500 for new valve guide seals on a 2006 550i. Problem is the labor. I was told it takes about 30 hours plus parts. Still, Ouch!