Anyone have any experience with filing insurance with USPS?

So I bought a pricy and beautiful poster from ebay. How much it was is irrelevant, but not something I’m going to let go.
The seller had like 10,000 sales with 99.8% positive feedback.
First of all, it took a while, a long while.

Got it today and the immensely solid cardboard tube had a huge rip/crack in it. The poster had several “dents” and color had worn off some places.
This was definitely not the sellers fault, it was obviously responsibly packed.

So anyway, I’m going down to the post office later and I’m wondering how easily USPS gives you your money back or if I have to take it to civil court.