Hi Josh - Not so much a "learning curve" here, than a "vertical learning wall" I think
The easiest way for you to get started is buy one of the excellent aftermarket books on the D300 (magic lantern guide etc)
In the meantime, if you look on the top right of the camera, just behind the shutter button, there's a button marked "MODE". If you press that, and simultaneously rotate the rear thumbwheel, you'll see the top display cycle through A, M, S & P (Aperture Priority, Manual, Shutter Priority & Program Mode)
Manual is just that - fully manual. Set the shutter speed and aperture using the thumbwheels.
Aperture Priority - You set the aperture you want, the camera selects the shutter speed required for correct exposure
Shutter Priority - You set the shutter speed, camera selects the aperture for correct exposure
Program Mode - You scroll through a selection of shutter speed/aperture combos that the camera has determined will give you the correct exposure.
There are no "modes" like you find on lower end cameras (sport, macro, portrait etc) You have to do all the work yourself
