1) Yes and noThey have new Chinese rolling stock. You're right all dining car service has been downgraded in Argentina. Best to take as much food as you can. Was it easy to get a ticket in the sleeper? And could you comment on the temperature in your compartment? I find trains here usually too warm.
2) Yes and no
To elaborate a little
I was out of the country at the time we made the booking. At the booking office in Retiro there was just one compartment shown as available but they wouldn't accept the booking without sight of my original documentation - which was out of the country with me. However, book on-line and they accept an uploaded document scan - reconcile that, if you will - and by the time we had organised all that and uploaded everything there was still just one compartment free.
According to the scrolling temperature guage at the end of the carriage it maintained a steady 19-20deg C in the sleeping car but once, in the dining car, the temperature climbed up to 25degC before it crawled back down again.