Battle: depends on what you mean by replace sound effects. If while casting Lightning2, for example, you want to replace it with the Luminaire sound, that should be possible by only changing 1 byte. A debugger trace should be able to track down where in the tech data a sound # is being selected. Replacing a sound with one from another game is a whole different story. They are in some synth generated format that isn't understood.
Music: a hex editor is required as mentioned above, TF doesn't support this currently. You'll want to know the start and end offsets of the SPC from the game you're copying from, and then copy and paste that chunk into a free spot in CT. Afterwards, a pointer will be need to be adjusted to point to the new SPC's location, and the instrument table hex values changed so the song sounds (mostly) correct.
