Unless you're shooting at the beach or on water, I don't think protective filters are truly necessary. Digital sensors are not as sensitive to UV light as film so I don't think they add anything to the image. If it's a cheap UV filter, its just another piece of glass in front of a higher quality lens element. This can only soften the image, or even cause vignetting, epsecially at wider focal ranges. In terms of protection, small surface scratches really don't show up in images, and if you bang a lens hard enough to break it, the resulting shards will probably gouge your lens and render it useless anyway. Use the lens hood...at least this will reduce the chance of flare and actually may improve your images.
The extra battery is a good idea. Also, look at picking up a speedlight eventually..the SB600 is cheaper and still effective, but if you've got the bucks the SB800 is a true gem.