Honestly, if you're just connecting from Amtrak to Amtrak, you'll go up an escalator or staircase, walk over a few tracks (maybe), and go down an escalator or staircase. Depending where you are on your inbound train and where the train stops on the platform, the nearest stairway may not even take you up into to the Moynihan hall. You could end up in Penn Station. But it wouldn't really matter. Presumably you'd need to be near the west end of the train to access Moynihan hall (front coming from Boston, back from Upstate NY).