Had to do this recently and found an easier way then what the FSM suggests.
1. Disconnect the negative battery terminal!
2. Remove the front skid plate. It is held in place by 4 12mm bolts.
3. Use a breaker bar to rotate the tensioner COUNTERclockwise. This is the only socket size i cannot remember. I believe it may be 14 mm, but don't quote me on that. Once the tension is released, remove the belt.
4. Remove the gray cap, and undo the 9mm nut towards the rear of the alternator. then remove the 2 10mm bolts near where the grey cover was. Toward the front of the alternator, there is also another 10 mm bolt holding on another clip. Undo that. Also, at this point, unplug the wiring harness plug that plugs into the alternator. Pic below.
5. Remove the two bolts that hold the alternator to the engine block. The bottom one is not visible in the below pic.(pic below).
The top one is 14mm, or 9/16's will work in a pinch. The top one is easy to get to. At this point, there is 1 bolt holding the alternator to the engine block. It may be helpful to have a friend nearby to hold onto the alternator for you. The bottom 14mm bolt that holds the alternator to the engine block is much easier to get to from underneath the truck, that is why I removed the front skid plate. Once you remove these two 14mm bolts the alternator will be free.
6. Pull the alternator out through the top of the engine bay. You will have to move a radiator hose and maybe an AC line out of the way a little bit to get it out, but it WILL come out this way!.
7. Put everything back in reverse order.
8. Pat yourself on the back, cause you just saved your self a bunch of money on labor!