If you are going in a sleeper you will enjoy a decent dinner. It is common to find Pasta, Grilled Steak, Chicken and Seafood on the menu. Breads, salads and dessert usually accompany the meal. I believe that Amtrak is using silverware, glasses and china plates at this time. At worst you'll eat off of a heavy plastic plate with Amtrak logo that looks just like a China plate (not a paperplate). Everything is served on a white tablecloth and the service is similar to a restaurant. Soda , Coffee, Tea, wine, beer and liquor is available (alcoholic beverages do cost a few bucks more). Breakfast is pretty much you would find anywhere, french toast, eggs, bacon,sausage, coffee and the like. The Amtrak website lists all the train menus.
We will be traveling on the Capitol Limited to Chicago in mid June but we are picking up the train along the way in Pittsburgh. We will begin our journey at 11:45 PM EST get to bed and be in Chicago at 8:45 AM CT. We have a 9hr :45 min trip, but going we have just enough time to sleep, eat breakfast, shower and get ready.
Be sure to see the great hall at Union Station when you arrive in Chicago but as you know Washington DC Station is most impressive. Have a great trip. BTW, if you wish to stay in downtown Chicago; many of the four star hotels are offering great deals right now on Hotwire and Priceline. We usually stay in the Magnificent Mile area and this year we are lodging at the Mellenium Knickerbocker. May accomodations can run as high as $250 per night in Chicago in May and $300 in summer, so shop around and you'll find great rooms for a decent price.