An autoshop will charge as much to fix as it would cost to buy a new one.
I hate sellers who mess people around like this. I recently got screwed over by a seller over a set of Vader armour, the set was smaller than his description (too small for me), I'd paid him extra to have it painted, when it arrived there was a patch where you could see grey undercoat under the laquer. He'd obviously run out of gunmetal paint and just decided to send it out in that condition. When I complained he just told me to send it back using special delivery (wouldn't accept a cheaper service even though originaly he'd set it to me using cheap standard parcels) and I'd need to send him the money to cover him sending it back to me Special Delivery. Took it to the post Office and they said it would cost me £25, so that would have cost me another £50 to sort out a set of armour that quite frankly I would end up selling as I can't wear it. I even asked if he could just refund me enough cash to cover buying the spray cans he'd used, at first he seemed to agree, but when I said it would cost £10 to buy the Halfords paints he told me 'to get lost'. Nice guy, hope karma gives him a damn good kicking. :angry
Did you use Paypal to pay for the item? If you did the seller has to use a shipping service with insurance, so either get him to claim through this, or complain to Paypal and they should get you a refund.