Thanks all for your great suggestions. I tried Theo’s approach and it worked well. For any other beginners out there, he’s exactly what I did.
1. Duplicated the video track. At first I couldn’t because I had the max of 4 video tracks already (for no good reason). I just deleted one of these and then Duplicate Track became active.
2. I put the duplicate track in layer 2, with the original in layer 1.
3. On the original track, I clicked the flim strip thing for “compositing mode” and chose Multiply (Mask).
4. From the Video FX track I dragged in the “levels” and the “color corrector.”
5. On “levels” I put the Gamma up to 2.1.
6. On “color corrector” I put the gamma up to 2. I also put the saturation up to 1.5.
The result looks pretty much like what Theo generated. Thanks again everyone for your help–the output looks much better now.
Paul.