It'd be difficult to pursue. Not only because of your proximity, but do to the fact there are likely no written contracts that would amount to much. It's more of a his word vs. yours scenario. I'm sure he asserts the amp was mint when he sent it out, but unless he recorded the amp functioning perfectly and then packing it up he has no proof. You also have no proof that the amp wasn't fully functioning when he sent it out.
I always record a playthrough of any gear I sell or trade. This guy is obviously shady because he's ceased communicating with you, but I don't know if that would be enough to get a court to order him to recoup the cost of the repairs and shipping. My fear is that you would end up out more money for court filing and travel expenses if you had to show up there to file.