I haven't ever bought from this seller, given though they seem to have authentic stuff, if it was fake there'd be more complaints, but what you can do is use this website to check their feedback, I find it very useful as it usually gives away if a seller sells fake things: http://toolhaus.org/
This is the link to the ebay section of the forum: http://forum.purseblog.com/ebay-forum/
What you can also do is search the ebay forum for the sellers name to see if anyone has complained previously or not
Perhaps a mod can move this thread for you and save you opening a new one.