Hi,
Okay -I've figured it out. Below are the steps that I used.
1. Go to the directory: C:\Program Files (x86)\Steam\steamapps\common\Pillars of Eternity\PillarsOfEternity_Data\data\audio\vocalization\vo wav files\player (Windows 8 or 7).
2. Copy the voice set that you plan to replace. In my instance, I copied all 72 instances of male stoic.
3. Create 2 folders on your desktop - POE Voice Set Original (backup purposes) and POE Custom Voice Set.
4. Paste the 72 instances of Males stoic into both POE folders.
5. You can then play all 72 sounds using Mozilla Firefox. Create yourself a notepad of the lines to use. For example: player_voice_set_m_stoic_0001 says "Yes." 0004 says "Sure."
6. Now you simply replace those voices as you see fit. I used Windows Sound Recorder to record myself acting out the lines and used this site : http://audio.online-convert.com/convert-to-ogg to convert my files into the ogg format that Pillars requires.
It's really easy to do. I tested them in game and it works fine.
Any questions?