>...the kit lens has an aperature >range of 3.5 to 5.6. Given this, why does the camera allow me >to select much higher numbers using the command wheel?
When the lens is zoomed to its widest (18mm), the maximum aperture is f3.5, but as it zooms out toward 55mm the maximum aperture becomes f5.6. Those numbers are the widest apertures you can get, and what you are seeing with the command wheel is that you can narrow the aperture with the command wheel when the camera is set to aperture priority.
>Second, and this will demonstrate my ignorance, what do the >numbers 18 to 55 represent, Is there a relationship between >these numbers and the aperature values?
Those numbers are the focal length of your zoom lens. 18 means when it is set there, the lens has a focal length of 18mm, so is a wide angle. 55 means the focal length is 55mm, so is a mild telephoto on your camera. You can see the effect by turning the zoom ring from 18 to 55 and watching the view go from wide to narrow.
Now, to your question, the lens is a variable aperture lens, so in aperture priority (A on the mode dial) set the lens to 18mm, and the aperture to f3.5. Then notice, as you zoom toward 55mm, that the aperture number will rise until it gets to f5.6, so there is a relationship between the aperture values (f3.5...f5.6) and the focal length (18...55). As the focal length gets longer, the maximum aperture goes up from f3.5 to f5.6.
But notice if you set your aperture to f8 and zoom the lens, the aperture remains constant at f8. Once you get the idea of what those numbers mean and what they do as you zoom, you can just play with the camera and lens and see how they work. I hope that helps!