You HAVE to complain to the seller, and see what he says.
:iagree This is the proper way to go about things.
I had an AUTOart Viper GTS-R show up busted. The vendor acknowledged the problem and sent me the money up front for shipping based on the post office's quote. I don't see why the purchaser should foot the bill for sending the busted diecast back.
Unless there was more to his message that you didn't include, I wouldn't leave negative feedback. Although there was a nasty tone to his message (at least that's what I read into it), he has offered to refund your money. Plus, if he hasn't left your feedback yet, he would probably use that as an excuse to leave you a negative as well. :mine