Ive been using Vegas Video since version 4.0; I currently use vers. 8.0 because of its stability. Vers. 12 looks like a winner so far and I imagine I'll eventually upgrade to it.
While I agree entirely with Chuckzootz, I suggest you try this work flow for best results:
1. Ingest your video. You should be able to bring .MOV files directly onto the timeline.,
2. Select "Black & White" from the FX tool set and take out all the color from the picture.
3. Turn on the Waveform Monitor and add "Levels" to the FX chain (the bar at the top of the FX window should show "B&W" with a check next to it, followed by "Levels.)
4. Using the Waveform Monitor, bring your whites up to 100 and pull your blacks down to 7. Tweak as necessary, staying within this range.
5. Delete the "Black and White" FX from the FX chain and close the Waveform Monitor (or move it out of the way.)
6. Now that you've set the low and high levels correctly you can go ahead and use the tools suggested by Chuckzootz.
One word of caution: Brightness and Contrast, a very powerful tool, effects the entire picture; in other words, if you use Brightness, everything in the picture becomes brighter. So it's not an effective tool if you only to lighten the sky and keep the brightness of faces the same. Before using B&C I'd go back to "Levels" and my Waveform Monitor and try increasing the gain, then tweaking the white and black levels. Trial and error and your monitor will get you to where you want to go.