With all the hassle you would have to go thru, it may be more practical to just cut your loss.
It cannot be proven if he knew it was bad or if the postal service damaged it during shipping.
I am not trying to sound negative, but I really don't care for e-bay.
Even if they have a lot of positive feedback, that can be falsely generated.
And then the seller could try some tricky crap like saying - "Well, it is your fault, it says in the ad that... (something bad)"