Lens length has absolutely nothing to do with the size of the sensor inside the camera body that captures the image. This thread concerns a larger solid-state sensor (translated as far more expensive) having better clarity and color definition compared to a smaller "crop" sensor (like your D7000 and most entry to mid-level dSLRs on down to P&S models) having less clarity and color definition when taking the same picture.

I think you will find that the camera will not be a long-term investment. Unlike the film cameras of yesteryear, digital bodies are replaced by new models about every two years. I have a D7000, and I'm looking forward to seeing what the D7100 will be like.

What people generally do is stick with brand and concentrate on getting good lenses. Cameras comes and go, but lenses are forever. That's where you want to avoid compromising.

As for deciding what camera to buy, I always like to read reviews by people who compare cameras for a living.

Camera Reviews
kenrockwell.com
dpreview.com
snapsort.com
http://www.whatdigitalcamera.com/equipment.html

Lens Reviews
http://kenrockwell.com
http://photozone.de/
http://dpreview.com

Info:
http://photonotes.org/articles/beginner-faq/lenses.html

This might seem like heresy here, but don't knock Auto. I leave my cameras set on Auto so that if something catches my attention, I can take a quick shot without worrying about settings. If the subject is still there, I can experiment.
Many times, I have found that the Auto shot was better than my experimenting in A, S, or M. Of course, for specific shots, aperture or shutter speed might be of prime importance, so then Auto goes out the window.

You can avoid lens flairs while shooting. The simplest way to see if you are likely to get a lens flare is to turn around, 180 degrees, from your shooting position and hold the camera out, away from you. If the sunlight is illuminating the lens, then, you have a good chance for lens flare.

If you have someone with you, simply ask them, when you are composing the picture, to look at your lens, and, above your camera, place a hand in the way of the sun, to cast a shadow on the lens. Bingo. No flair possible. Lens shades help, but are not a complete solution. A hand, a hat, a clipboard, a magazine... anything that can cast a shadow on the lens... these are the tricks of the trade.