I have an '05, but yours should be the same. Behind the tow hook, and the same place on the other side, there is a small space to fit your arm back there to change the bulb. The best way to do it is to go under the truck on your back head first, you won't be able to see, so feel your way to the light. Use your right arm to change the left light and vice-versa.
FYI: Wear a old long sleve t-shirt so when your done, your arm dosn't look like you got in a fight with a cat.
This way is much easier than to take out all the screws on the fender well.