As another tip, it doesn't hurt to ask (in German) if the seller will ship to the USA via German Airmail. There are also sellers that will accept PayPal, once confirmed.

There are two headaches with E-Bay overseas. First is that anything other than German Luftpost is damned expensive. FedEX and UPS for a 7 kilo box is over $100. Second, if you have to wire money to the seller, your bank or Western Union is going to add about $35-$40 to the transaction in fees. Always make sure to check if the bank that you're using routes the wire transfer through any other bank that may be adding another fee. It's common for US banks, wiring dollars through to Germany, to use a UK bank along the way. The UK bank will deduct its charges from the wire, meaning that your seller may not get the full amount.

As you can tell, I've done this before.