Car shop messed up my new car. Who s response?

I JUST bought a used car, clean title and in good condition. Its a 2007 honda accord ex. Friday, The very next day, (Saturday )I took it to a reputable place to get an expensive $300 viper alarm. Well while they were working on it, 4hrs. Later, the told me the car didn t want to start. The manager told me that what happened was that while the car was running, the battery died cause, "it was low" well anyways, to try and restart/jump start it, the used a "jumper box" and well, must have had it on high or something, cause it completely "fried " my ecu and they needed to order a new/used one to replace mine.
So devastated, I got a ride home. And on monay morning, they had it towed at their expense to a mechanic. He ordered the part Tuesday, received it "Thursday " and hasn t been able to fix my car.
Desperate to get my car up and running, I called and asked about it, and it seems like he can t figure out why the new "computer" doesn t want to take a code. I don t know. The manager at the alarm shop feels so bad, he offered free window tint service.

My point, I m fed up with not having a car, if I take it to my own mechanic (honda dealer) will he still be responsible for fixing the damage to my car that his own mechanic can t fix or figure out? What are my options? Cause I ve been nice enough to to let him take it to his own shop of choice, but enough is enough… They are getting no where and I need my car! Please help me. What would you guys suggest I do? I m desperate.

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