Yeah, the Serpentine isn't that difficult to replace. It's easier when you got a buddy to hold the breaker while you feed the belt around the pulleys, but it can be done by one man. Be careful too, that spring in that tensioner is pretty strong and if you let go of the breaker you could whack yourself pretty good.
Now don't be alarmed about cracks going across the ribs of the belt. That's normal and your new belt will get them rather quickly. My belt got them in a couple months. Cracks going parallel to the belt or on the smooth side are signs of imminent failure.
Now the ONLY thing that'd make replacing the belt on a Gen 1 Explorer easier would be if the tensioner had the square drive hole like the newer trucks and my Powerstroke.