Can I change the firmware of my camera or add features somehow?

So I have a Nikon D3000. I try to do HDRs but it's hard because the D3000's firmware doesn't have an exposure bracketing feature. Is there any way I could load a modified version of the firmware onto the camera? And if so where could I find it?

You don't need exposure bracketing to do HDR. Put the camera into manual mode - then adjust the aperture/shutter speed until your meter reads +1 (take a photo), 0 (take a photo) and -1 (take a photo).

Also, you can use exposure compensation - even in Auto mode. Just set compensation to +1 for the first photo, 0 for the second, and -1 for the third.

In reality, I rarely use exposure bracketing - it is usually more trouble to setup than simply doing the above alternatives. The only real benefit to bracketing is if you have to rapidly take 3 photos, as it takes slightly longer to set exposure or exposure compensation than bracketing.

Modifying firmware is one sure way to kill your camera.