this can be done but only in stereo if totally in the digital domain. So you would have to send different parts out in real time to wave edit then wave mix on the pc. I think it would probably be easier (certainly quicker)to use the mixer and effects on board, but it is an option if you have some 'must have' effect on pc not on the 7000.
mp3 playback is mp3 playback - as long as its a mp3 it should work.