Aside from the engines and baggage car, always a the front, the consist order is:
Trans Dorm
Sleepers (2-3 depending on season)
Pacific Parlour Car
Diner
Sightseer Lounge
Coaches (2-4)
What do you mean by OBS? And Observation or "Obs" car? Frequently the Sightseer is referred to incorrectly as the Observation or Dome car. Observation cars were cars on the rear of the train with a lounge at the end. Older obs often had open platforms, streamline obs had finished, often rounded ends. Dome cars had domes that were above the normal level of the train car and offered forward and rearward views. Technically, there are no obs or dome cars on any Amtrak train, except when they carry private cars or Amtrak's single remaining dome, the Ocean View. I don't say anything to other passengers onboard when they say Observation or Dome car in reference to the Sightseer, though. I reserve that to this and other RR forums, since these forums are full of railfans. To be completely proper the "Parlour" isn't a Parlor car, either. It's a first class lounge. A Parlor was a first class reveneue car for day trips. In the traditional definition "Acela First Class" is a Parlor service, although they'll never call it that since it sounds antiquated even to my ears.
The conductor and assistant conductor walk through the train often in the course of their duties. Sometimes they'll stake out a table in the diner other than at meal times, or in the lower level of the Sightseer lounge, to do their work. Late at night, the conductor can often be found at a table in the diner.