If Dublin is not too far for him, check out Mike's Car Clinic on Yelp.com. They got good reviews. I only went there once and they seem to be reliable. They have another shop in Concord, but I think Dublin might be closer to Oakland.
If you are looking for a Subaru only independent mechanic there is TD Garage in Walnut Creek. I haven't used him but have talked to others that have and they seem to be quite happy. He has a Facebook page so you can find him there.