Disklavier

I'm considering the purchase of a Yamaha DGC1A Mark III Disklavier 
5'3" grand.  I'm curious about how the piano will handle MIDI 
files.  I believe it will play the piano information acoustically, 
but is this only if the piano part appears in Track 1?  I have 
several MIDI files where the piano part is in Track 2, or sometimes 
the left hand is in Track 2 and the right hand is in Track 3.  Is 
there a way to get the Disklavier to play any track you wish 
acoustically (rather than reproducing it as a synthesized sound 
through the speakers?)

Also, just out of curiosity, what is the difference between the 
information contained in a MIDI file's piano track, and the 
information contained in Yamaha's PianoSoft-format files?  Does the 
PianoSoft format capture more subleties and nuances of the 
performance?

Thanks in advance for any info!