For over 30 years I operated only in manual mode on film cameras. I rarely used cameras with auto exposure. But the world changes and so have I: now I rarely use manual mode. With today's cameras, the "P" mode uses the same rules I used to use manually.
There are photographers who NEVER use P mode, and it is always worth learning what exposure actually is. As spraynpray states, you might be better off using manual mode for a month or so exclusively to get an understanding of what life was like back in the days of the Leica M3 or Nikon F2. BUT you will miss a lot of shots. With the D7000 manual mode shows you an exposure meter, so it isn't really the same.
Since you don't mention P mode in your post, maybe you should review its features:
When using a D7000, the Program mode controls only the shutter speed and aperture using the old rule that it will pick the best combination trying to avoid exposure times that are so long they risk camera shake.
Everything else on the D7000 can be changed by you. Normally you would make changes in this order: Meter first, check for necessary exposure compensation, check for proper ISO, and cycle through the reciprocal exposure equivalents with your dial, then take you shot.
Since I come from a film background, I am more likely to stick to a set an ISO first, but on the D7000 it might be better to meter first, look at your settings and decided if you want to increase your ISO after deciding if you want to use exposure compensation or not.
You then set exposure compensation to help with blown out or under exposed areas.
Finally, if you are not happy with your Program mode choices of aperture and shutter speed (which show up when you half press the shutter) you can change them by rotating you dial to cycle through all the equivalent aperture and shutter speed combinations that will give you the same exposure.
This procedure is the functional equivalent of Manual control, but you don't lose shots to bad exposure from mis-metering.
If you really want to try manual mode, set your camera to ISO200, tape this guide to the back of your camera (you wont be able to see the LCD anymore) and use these or their reciprocal settings to set your camera.
