Disklavier

Hi.I know i have already posted this question but i had no answers...
I got a little C110 disklavier Mark III, and a Mac G4 with Mac os X  
10.4.7
I want to modify midi files from the web which doesn't make play the  
piano (by moving track on the first or second pists of the 16 pists),  
I don't find what soft can do that (and also change some  
instruments... sometimes there is a poor harmonica for the singer  
voice and i want to change it in order to be played by the piano!)
Moreover, I'm searching a soft which allows to scan sheet music, and  
convert in standard midi file to be played by my loved disklavier! I  
know there is smartscore but i have tested the demo which is plenty  
of bugs... Do you have the real version? Does it work?? (300$ the  
software, if it's bugged, it's not cool!)

Thanks for your answers!
Please excuse my poor english!