Will sharpening broadheads untune my arrow spin? I'm shooting Thunderheads and have taken about 20 shots w/ each head at a styrafoam(SP) target.

Your tune shouldn't be affected by sharpening the blades. As long as you don't remove a lot of material and unevenly.

No, not at all, just make sure to take the same number of strokes on each edge. But, if you are only practicing with the heads right now, I wouldn't do anything. Sharpen them before you hunt.