New Airport Express and old airport extreme

Hello,

We have a cottage next to us for rent and I purchased the new Express in order to utilize the "guest" feature. Can I use the old Extreme to extend the range from our house to the cottage and link it up with the New Express?

Is it something as simple as "extending the network"?

If so, will the guest feature still work if the old extreme is located at the cottage but using the new Express "Guest" feature at our house?

Thanks for your help.

John