I have a 2000 PSD 6-speed. Granted it is a 7.3 instead of the more powerful and more efficient 6.0 but to comment on the transmission (which is likely identical) it is awesome! I am a die hard gearjammer, the last 5 trucks I have owned have been stick shift and this one is without a doubt the best transmission I have ever driven. As Michelle stated there is a granny gear which on my shift pattern is labeled "L" and then there is 1st - 5th. "L" is a great off-roading gear when you really want to "crawl" in tight, tough or limited visibility 4-wheeling situations. It is also useful for starting up a steep grade when you are towing. I have done a lot of towing with this rig and the upper five perform wonderfully for all normal around town and highway towing work. I pull a travel trailer that weighs about 5,000lbs. and have no trouble pulling in 5th gear at highway speed (65+). From my place in Pasadena, MD (just south of Baltimore) I pulled to Lancaster, PA using cruise control full time on the highway, 5th gear, AC for the whole trip. There are a number of decent grades between here and there and this rig only dropped cruise control on two of them. It drops the cruise if it looses 5mph below set speed.
God Bless,
-BunnMan