If you start fixing on the car yourself they are going to claim that you caused the trouble. I would leave it alone and take it back to them and tell them to fix it. If it was paid for with a credit card I would put in a claim with them to stop payment.
Your bill is scary you could have bought my car (I paid $2000) 2 X over and still had cash left over to fix them.
If they will not resolve it with you; most States have warranty laws and from what I have seen on Court type TV is that if the shop could not do the job correctly they were supposed to tell you they could not do the job and refuse to do the job.

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84 300D, 82 Volvo 244Gl Diesel