Have repairs done through my insurance company or the other "at fault" party's?

DO NOT CASH THE CHECK, GO THROUGH ALLSTATE like the shop said, this way your car is fixed right, and allstate will go after the other insurance company. Typically those cheapo insurance company send a check that is too low, if you cash it, then you accept their offer. It sucks, but thats how that other insurance company makes millions of dollars, by screwing people like you. Im not clear where your dilemma is, you should have already notified allstate when the accident happened, as they would be working on your behalf now?? did you not bother to call allstate or what.?? do what the repair shop told you, they know what is right, and now so do you. good luck dumb *** kid needs to park his phone in his kazoo first then drive.