I might be concerned with what the store means by Demo. If it in fact is a store demo, it could be abused or very dirty inside if other store demos are any indication. It might mean a return-to-stock camera from its on-line shop which could be an indication that someone bought it and returned it for reasons unknown.
Other than that the D7000 is a stable well sorted out camera. The only one of real concern might be the oil droplets from a defective motor seal that a few forum members had. The intitial AF problems usually turned out to be the camera just needed to be learned better but a few needed calibration. Mine was excellent but suddenly developed a problem with AF on wider lenses only during an event. I took it to a Nikon warranty station and they adjusted it back to proper adjustment last May. The over exposure complaints that a few expressed were not camera problems but learning a slightly different bias towards preserving more shadows since the camera had a wider DR than any other DX camera. Even with the extended DR, many scenes are wider in tone range that what any camera can capture without data loss at either end of the amplitude range. That change in the metering was a good thing and you will find the metering to be quite good when you get used it. Unless your prior camera was a D3x or D800, at low ISO, the D7000 will be a step up in DR. If something does not seem right based on prior experience, just ask on the forum. We have probably heard it before and can suggest solution. One thing right off, consider increasing shutter speed on hand held shots for best crispness of images. The old rule of thumb of 1/(FL*1.5) for hand holding might be the minimum unless you have excellent hand holding technique. I use 1/125 minimum for hand holding my 85 1.4 but prefer 1/250 if the light is good enough for still subjects. Action shots will be higher of course. Good luck, it is an excellent camera. Stan St Petersburg Russia