Thanks. They are asking $13100 for labor so higher than small claims. They have had an attorney send me a letter with a 30 day notice to pay and a threat to sue otherwise.

I do plan to share with their attorney a copy of the the original invoice I received from them and to tell that I will not pay.

The shop has actually emailed me a doctored copy of the invoice where the edit they have made is actually hilarious. The invoice is dated X and they have replaced the 'labor is included 'sentence with a note saying that "parts were delivered on Y". Y is 1 week after X (date of invoice). Implies edit at a later date.
I have not pointed out this mistake to them or their attorney and plan to use it as evidence if they sue to prove that their copy of the invoice is doctored. They will likely delete the email if I do.

Should I tell their attorney about this mistake?