Dropped my Nikon D40x, Pictures dark, won't let me go into manual settings.

I recently dropped my Nikon D40X from a fairly good height, nothing is damaged from my understanding, the lens is intact, shutter is perfectly fine, but I realized afterwards every single one of my photo's that I try to take, turns out EXTREMELY dark! I read some articles and it said to reset the camera settings, well when I do it, it dosen't really affect anything, and I try to go into manual mode to change the aperture and the shutter, and it won't let me change anything, it stays in auto.

Does anybody know a solution, or solution(s) that I can try to fix my camera by myself? Or would I have to take it in to get looked at?