Sony Vegas VS After Effects for graphic / Keyframe editing
After Effects is definitely the right tool to use rather than Vegas for motion tracking / drawing on moving footage. Here is a classic tutorial that you can watch to get a sense for how to achieve face tracking &amp; replacement.

Vegas is much better suited for editing. After Effects can often struggle to achieve real-time playback over extended periods of time and doesn't have the tools built in the same way as a NLE like Vegas, Premiere, or Avid.