Ebay Troubles..., What can I do about this? Options

[Yota]

A few weeks ago my mom backed into something that cracked her taillight lense. In order to save her a few dollars (ultimately a mistake), I bought a taillight off of ebay. The description said it was used, but in good condition with only a couple minor and repairable scuffs on the lense. When I got it today, there was a crack on the side of the bezel that pretty much renders this taillight useless. It will leak water into the housing. My mom is not satisfied with this. Neither am I.

So I emailed the sender and told him about it. I told him I will send this back and expect a full refund of my money because no where on the description does it say anything about a crack.

My question is, how difficult do you think this will be to get my money back and send back the taillight?