Well,
Audacity has functions that allow you to change the tone of a recorded voice.
MefuneAkira made a great tutorial, which you can find
here. I believe it includes instructions on changing the pitch etc so you can deepen your voice.
Your other option is to enlist the help of others. On the
TMU forums there should be people willing to give you a hand with VO's.
The only thing worse than beating a dead horse is betting on one.