I bought my car 300 miles from home, but my local dealer (5 min drive) has a fantastic service department. You'll know you have a good service department a lot of the time by getting a service writer's business card and just chatting with them about potential issues. If they are friendly and actually take time to listen to your concerns, and have numerous ways to contact them on their card, you're likely to have a dealership that cares about getting the job done right.
Also read reviews like Angie's list and whatever you can find on Google. Negative reviews are likely to be more prevalent than positives, but the one with the least negatives/most positives is likely the one you want to go to, adjusted for dealership size, of course. Smaller dealerships that are family owned and not part of a huge chain like Dobbs will also be more likely to do better work. Big chains don't care about reputation or their insurance claims/rates as much as mom and pop shops.