I lost my cd case for Diablo2 and cannot play this $50 gem that I purchased. Blizzard wants me to write an essay on how I lost the key and then send it with my original play CD and ten bucks for ...

I've been starring at Google for HOURS, trying to figure this out.I have two copies of Diablo 2, one of which I sold. I am going to send the CDs to the buyer, but I am not sure which key to send ...