Maybe try Capital Airsoft or 007. They could probably repair it and write a quote AND they're actual storefronts so could give you a legit and professional looking repair quote.
I'm also surprised that the package was opened. Doesn't that kind of imply someone knew it was an airsoft gun and played around with it before delivering it?
I would inquire about that since it's a federal offence to do such a thing.
Also what method of delivery did you use? IIRC there are two ways to ship one being it's contracted out to the lowest bidder and the other is actual CP guys who deliver.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE