1 - Paypal and Ebay both prohibit all transactions with Nigeria
2 - You are never asked for a shipping number before getting the money, you got a spoofed Paypal email http://consumerist.com/2008/10/how-a-nig…
3 - Paypal NEVER uses Western Union and there is NO such thing as a Western Union Bank
4 - the RECEIVER pays customs charges, never the sender.
You got scammed. There is no buyer and you did not get paid
Rule Number One of Paypal is that you never send your item until you go to Paypal.com and verify the money is IN your account
Unfortunately the scammers target new Ebay sellers with fewer than 10 transactions as they are usually unsure how Ebay works
Report this ASAP to Ebay but your lens is gone and whatever money you sent is gone. Also file a police report