I think you might be able to request general auto registration data from the local government. Less formal but potentially more effective, check in with owners clubs in your area or scan mall & restaurant parking lots.
Best bet, start small and leave room to expand (e.g., start with one bay, basic equipment, and very little inventory). No need to drop your whole nut right away.
One thought, put out feeler ads or post flyers for your services under a generic name with phone/email info only well before you're actually ready to officially set up shop. See what kind of response you get and use that to dictate how big you want to go up front.