and only the top half of the headlight illuminates. If I look at the my headlights straight, the bottom part is blank and no light coming through...anyone know why?

 

You have to make sure the bub is straight and level, make sure to turn it until it "clicks" into the correct notch when installing. Even if its not installed correctly, the retainer clip will still fit around it, so take it out and try again. If its not straight and level, it will project the light either too high, too low, or too much to the left or right.