1) I would think that in order to re texture a item. You would need to match up the coding name that is previously saved from the old one. Say you want to change a texture to something else, you would replace the old texture with the new one but save it under the same name so you don't have to mess with changing the texture name in the coding for the items.
2) Regardless on whether items you do get, you can have as many as you really want. But if other people don't have the same items/ coding package as you have, then they will see something else.