Hi Vintagelady,
I've just been added to eBay express. I've been waiting to get 100 feedback so that I could, but eBay didn't notify me once I was added either, which they with any new add, at least with a letter of info about it. So I'm also having to do my own research.
So just as an FYI, although you may find it a great extension of your store and another good way for customers to find your product, I do know so far that you can take yourself out of eBay Express if you'd like. The option's in your eBay Preferences under "Selling Preferences" where you'll also find a link to "Learn more..."
Hope this helps!
~Dee