You can see the layout of the Superliner Sleeper here (or Google can find you more images):
http://trainweb.org/andy/images_jpg/...nerSleeper.jpg

It's not possible to see where you'll be in relation to the dining car, because there's no way of knowing whether the sleepers will be in the front or rear of the train. (The dining car and Sightseer Lounge will be in the middle.)

You should research your choice of roomettes. Check this thread (among others here) for some recent discussion:
http://www.flyertalk.com/forum/amtra...signments.html

Meals are included, but you can't order multiple courses. Alcohol is served in the dining car. If you bring your own, the rules say you must consume it in the roomette.

Enjoy the trip!