Yes - you can adjust the Sharpness of your picture control settings. The Picture Control settings are described beginning on page 147 of the D300 manual The adjustments are specifically described on page 150.
Simply select the picture control that you want to modify, and then adjust the Sharpness slider to taste.
Be careful about overdoing sharpening. It also creates noise when pushed too far. The in camera setting is pretty heavy on the Radius and somewhat low on Intensity. I find this works well when used lightly, but not so well at higher levels.
If you are doing a full edit in Capture, you probably want to set in camera sharpening lighter or remove it in an early editing step. You might also check your setting for Contrast. Many times a little more contrast is what is required.
Also check you camera's setting for noise reduction. NR should normally be lon Off or Low. NR works by softening the image. It's more effective to apply NR selectively in post process. The Capture NX2 Noise Reduction function is pretty easy.
Joseph is correct. The picture control settings are in the NEF and some software does use those settings. The Nikon products - View and Capture - as well as Photo Mechanic. And all these programs can be used to create TIFF files that incorporate the Picture Control settings for use elsewhere.