Nikon DSLR DX format lens to FX format body?

Nikon DSLR DX format lens to FX format body?

Full frame Nikon Cameras (FX) automatically crop the sensor to accommodate DX lenses.

You will get no more vignetting when using a DX lens on an FX camera than you would using a DX lens on a DX camera.

When I need more reach and want to be able to frame the shot in the camera, I tell the camera to use the DX portion of the FX sensor. Otherwise I can just crop the full frame image file later

Nikon is smart about this. If you use a DX lens on a FX body, the body will know about the DX lens and automatically crop the image so you won't get vignetting.

No.

The DX lens will not project an image large enough to cover the FX sensor. You will end up with small pictures that have large dark fuzzy borders.

Beware. DX lenses have protruding rear elements that can break your expensive full-frame camera's reflex mirror.

At the long end of the zoom you will probably not get much vignetting. But if both of those lenses are specifically designed for DX then there can be no guarantee of lack of vignetting.

Why are you interested in making the change to FX? Does your D7000 not give you what you want? In what way do you think your photos will improve by moving to FX? Do not forget that it is the photographer who makes the photo.

Your 50mm will be fine as it's an FX lens. Nikon doesn't make a 50mm DX lens.
The 55-300 as John P wrote will be problematic and you should sell it.

So the Nikon D750 got me interested.
I've been planning to buy one, until my D7000 can be sold.
First of all, I have extra DX lenses; 3.5 55-300mm and 1.8 50mm. I heard it will vignette if partnered with an FX body, but is there no exception on a zoom lens even if I zoom it to the closest/biggest focal range possible?