One bolt holds the tensioner arm on the engine (center of the tensioner pivot point). Once that's off you can remove the pulley from the arm (a torx head bolt, I think). And when you put the arm back on the engine, there's a locator pin, so it will only go on one way (and torque the bolt to 30 ft/lbs). There isn't a torque spec for the pulley bolt, since Cummins considers the whole assembly as a replacement item.
I just replaced my pulley at 125k miles, and it didn't feel worn at all. But I'm sure that varies with the truck's living conditions.