Kawai Synthesizers

My uncle gave me one Gmega Kawai module. I have one Yamaha PSR-520 
and I tried to use Gmega. Nice sounds, but all general MIDI sounds. 
I have Midiquest Xl 9 and I try to edit sounds. Is there one site 
with help to set up sounds like "depht, shape" to create new sounds? 
I want to create nice piano sounds and electrical keyboards. Can I 
use the other sysex (roland, korg) to import to my gmega? Can I put 
really nice polyphonic sounds? How?

Thanks to help me.