Send the label but do not accept the return.
Ask the buyer to use the original box and packing material. Not critical but it helps.
Wait for it to come back.
Check the board.
If it's not yours, file an appeal with ebay. You have a 50/50 chance on the appeal.
If it is your board, accept the return, refund the buyer, and file a claim with the post office. You'll need the original tracking number and the ebay transaction report showing how much was paid. Take it into your post office to file a claim. They will issue you a check for up to $100 for the item, less the shipping cost. You have to turn over the damaged item, so it may or may not be worth it.