This is all about AE technique. No fast 'n easy plugins. No handy scripts. TECK-NEEK.
Make two text layers: one upper-right, right- justified. The other is lower-left, left- justified. You useSource Text keyframes to change lyrics combined with a set of opacity keyframes. You change the Source Text at zero opacity.
Naturally, you'll want to find the points in time to make the changes. You do this by scrubbing audio, then previewing small sections as you go along by changing the Work Area. I WOULD NOT use mp3 files -- too unreliable. Convert them to wav or aiff files.
If you're fast & accurate, you should be done in about 8 hours.
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA