Is my small claims suit on defective auto repairs legit?

2000 Corolla with 140,000 miles, check engine light, rapidly blinking turn signal. I asked the shop to look it over carefully, run diagnostics, and advise on whether it's worth putting money into it hoping it will last past 200,000 miles (these cars often do). Their estimates to take care of the check engine problem by replacing the fuel pump, struts, and other repairs was $2,100. That stretched the envelope, but it's been a great car and I said to go for it. They replaced the valve cover gasket, replaced bulbs and a flasher unit, did the suspension work. The check engine light came back on. They replaced the oxygen sensors. The check engine light came back on, and in addition the turn signal switch started buzzing loudly. They replaced the turn signal switch, and cleaned the mass air flow sensor to take care of the check engine light. They commented the catalytic converter was on its way out.

The repair bil quickly went over $3,500 and climbing. The check engine light came back on (always on the way home). I decided to run like mad from the shop. They didn't fix the check engine light problem, and every time I walked in the door something else went wrong with my car and it cost me hundreds.

A month later my car acted up again. The new shop had to replaced the valve cover gasket, and commented it had been incorrectly repaired. They also replaced the mass air flow sensor. Finally the check engine light stays off. The second shop's bill was $700.

I took the $700 invoice into the first shop and it was not a pleasant conversation. "That's why they call it an estimate," "we can't be responsible for an old car when things break." Estimate $2,100, paid $3,500, and there were more repairs coming down the pike.

I'm suing in small claims court. I'm not claiming intentional fraud. I think they blew the initial eval, and they didn't know what they were doing with the engine diagnostics. They were just checking things and replacing them hoping it would work, which it didn't. The owner of the shop was also angry I didn't take it back to them when the valve cover gasket started puking oil again. I said "I don't trust you." That's when the conversation went downhill.

Think I have a case? Their suspension work seems to be fine, so I'm not going after that. But I am going after all the engine and electrical work they did. The last time my blinkers started going fast I replaced a bulb and it fixed it. They replaced the flasher, then the lever mechanism for hundred of dollars.