Tony,
I've never owned a D70, so I don't know its particular idiosyncrasies. However, based on your postings that I've managed to get to, I don't believe that your camera has any special problems aside from being old tech.
Take my advice for what it's worth, but if I were you I'd do three things before looking at a new camera body:
1. Take more of an active hand in setting your EV compensation based on the scene. If you have to, do the old chimp, adjust and reshoot.
2. Shoot RAW
3. Make a serious effort to learn how to do the basics of RAW editing, especially managing exposure in post. You might need to do some homework about which piece of software to use. We can help there.
I'm by no means an expert, but all of the problems you've described that I've had time to read can be explained by exposure problems and the camera's JPEG processing going a little too far with contrast and saturation. If you take more control, I think your D70 might well deliver much more than you thought possible.
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