What game(s) except FF3us would/do you like to hack?

The only thing i miss is being able to build up some decent/nice music starting from zero... besides i dunno which tool should i have to use for it and which music format should i use.

I'm not a musician but I know music is an universe in its own. Get piano lessons and learn your scales, then move on trying doing arrangements with Reason or Cubase. If you want to compose you'll need at least an USB musical keyboard that you can connect to Cubase or other program. But seriously before you get decent and original results, you'll have spent a lot of time learning and composing.