I used to sell on ebay back in 2004-2006 using a drop shipping method with a distributor. Back then every time I made a sale I would log into my paypal account to find their address and ship their products. I used the upc code, a shipping code and their address and upload it onto my distributors server for the order to get shipping. In 2013 I am looking to get back into selling on ebay and maybe amazon in the future. But what I need to know is how do big companies on ebay sell 1000's of products? I know they can't have someone doing what I did in 2006 to process orders. I have been looking at oscommerce, auctionblox, vendio and frooition and its all very complicated to process. An example on ebay I saw a store called: http://stores.ebay.com/MovieMars and they have well over 300,000 products listed. What internal systems do they use to process all these orders on ebay? I specifically need to understand how I can get the buyers address, shipping code, product upc without me doing it manually from paypal. Basically how can I produce files/associate ebay listings with upc codes and have a file ready to download? Right now I can start selling items by listing them using Turbo Lister like I did in the past but I am looking for a hands-off method. Thanks for any help.