It sounds like you wish to EQ and Compress your Audio stream. Those Effects are limited in PrPro. I would look into either Audition (my choice), or Soundbooth. AE is for compositing images, and while it does handle some Audio, is not an Audio editor.
You can use Audacity to record you voice - http://audacity.sourceforge.net/
export Audacity audio file (your voice track) as an MP3
Import this MP3 into PPro
Lock video track and delete original unwanted audio track
select your new mp3 and paste to time line of the deleted audio track
Test and adjust if audio needs to be In-sync etc.
When happy with new audio track and video unlock video track.
Locking the video track allows just the audio track to be edited.
I would strongly recommend against using MP3, as the Save_As format, unless one wishes to loose most of the fidelity.
PCM/WAV @ 48KHz 16-bit would be a much better option, and no compression loss.