The store at Downtown Disney is Wonderful World Of Memories. you can buy most everything at the resorts and parks though.
They have some stuff, nothing to write home about though. I get most of my Disney supplies from mousememories.com. They have a great selection.
If you are using a post bound album or a strap hinge album you can add refills, to an extent. They don't hold an unlimited amount of pages. I think I have 45 in one book and 50 in another.
Not all refills are universal though, so make sure you get the ones make for that particular album. I haven't had very much luck finding refills in the store for the Disney albums, but I haven't looked online. And the albums sold at WDW do not have refills. If you buy one of those, take all the pages out and buy all the same to complete your book.
I started scrapping with our first WDW trip, it is sooo addicting! I have 2 albums for that trip and I am now working on our second trip, which will also be 2 albums.