The cars on the Chicago to Seattle Empire Builder are bilevel Superliner cars, but Ive never ridden in them so I dont have experience on what they are like, but I hear nothing but praise about them.
Detriot to Chicago is a bit different experience. They use single level Horizon coaches. I DO have experience with these .. . and well they are certainly nothing special, so dont expect much in the way of comfort with these cars.
Food, the Empire Builder has a dining car serving complete meals. Amtrak generally serves great means with pretty good selections. It also has a lounge car for purchasing snacks and suvieneers and stuff like that.
Detriot - Chicago. Probably an Horizon Dinette or Amcafe. Sells light fare snacks, sandwhiches, and beverages! Some of which is pretty good from my experience.
Food is quite expensive on Amtrak trains, or at least it seems it to me!