You need to check on your local small claims limit, and while this likely exceeds the amount, you may want to limit your suit to the limit of that court since you will not need an attorney. You're going to need an automobile expert to testify that the work was performed improperly and that you were overcharged. Not an easy case, even with an attorney.
If you'd like to discuss, please feel free to call. Jeff Gold Gold, Benes, LLP 1854 Bellmore Ave Bellmore, NY 11710 Telephone -516.512.6333 Email - Jgold@goldbenes.com
Your best bet is to contact an attorney in your area-- take your documents, voicemails, notes, bills, invoices etc to that attorney and consider filing a suit after discussing you options. Much will turn on the contract you signed with the facility, the written estimates they provided etc.
READ THIS BEFORE CALLING OR EMAILING ME: I am licensed to practice before the state and federal courts in Virginia. We have not established an attorney-client relationship unless we have a signed representation agreement and you have paid me. I am providing educational instruction only--not legal advice. You should speak with an attorney to whom you have provided all the facts, before you take steps that may impact your legal rights. I am not obligated to answer subsequent emails or phone calls unless you have hired me. I wish you the best of luck with your situation.