A couple of weeks ago, I purchased a used version of the lens you're getting, and have been so happy with it.

For best results, shoot in enough light that you can keep the ISO around 200. If you aren't familiar with exposure, a book highly recommended on this site is Bryan Peterson's "Understanding Exposure."

For example, you will want to learn how a fast shutter speed is important when capturing moving birds or animals, and how a high ISO will make your images look grainy (digital noise) and affect overall sharpness. The third element is aperture (f/stop), which controls your depth of field - how much of your image is in focus from nearest element to the furthest.