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You can do this alone in small claims court. Here is a link to the Miami-Dade Court Clerk's Office that tells you what to do to file a claim: http://www.miami-dadeclerk.com/property_small_claims.asp
Your suit would be for breach of contract and property damage. The shop's failure to do what it promised in the breach of contract, and this breach caused you to suffer property damage to your car.
You'll need proof of what costs you incurred because of their actions.