What you are describing sounds like you have a great lawsuit.
However, you are limited by the "damages" you can prove.
YOu have to be able to prove how their treatment (the poor treatment you received) harmed you. That limits how much you can receive in a case like this.
And generally speaking, you can not sue for attorney fees.
So you may be best of using small claims court.
Small claims is a true "peoples court". The formal rules of evidence and procedure do not apply. So you can represent yourself (no need to hire a lawyer).
The process is simple enough. You head to the county court (the county where the shop is located) and talk to the clerk of the court. They can get you the forms needed to start. You file the claim, serve a copy on the defendant and wait for your day in court.
In court, be prepared to tell the judge what happened, and bring in copies of any evidence that supports your case. IF there are witnesses who can testify about what happened? Have them come as well. Here, an estimate from another shop on the cost to fix this would help you prove damages.
Please let me know if you have more questions. I am happy to help if I can. Otherwise, please rate the answer so I may get credit for my work.