If you are taking your quilt to a longarm quilter, you do not need to put the layers together. The quilt and backing will be loaded onto a frame. For preparation you should trim or remove all loose threads, and press the top. When pressing the top, make sure you don't have any tucks at the seams. Have your seams pressed to one side if possible. Press the backing fabric. Be sure to remove any fold lines in the fabric. If you furnish the batting, and you are using packaged batting, take it out of the bag, unfold it and let it "breathe" for a couple of days. On the label that is up to you. Unless you intend to enter the quilt in a show, it isn't necessary to list any reference materials. If you do intend to enter the quilt into a show, be sure to tell you longarm quilter and find out what her requirements for show quilting.
Hope this helps.