I don't usually work on this engine in my 2000 Ram van (conversion) with 3.9L V6. But I should be able to handle changing the tensioner pulley, which is starting to whine. The engine compartment is cramped. Can I do this by just slipping off the serpentine belt? Or do I have to remove other parts, i.e. hoses, fan covering, radiator or more? Are there any "gotchas" i.e. left-hand thread on any bolts to trip up the adventurous beginner? Or is it straight forward and simple?

It should be very straight-forward, where you start by removing the serpentine belt. With the right breaker bar, you should not have to remove any of those other items. There are no left-handed bolts. Afterwards, tighten the tensioner pulley bolt 20 lb.-ft.