I wanted a 6 speed when I bought mine, but am glad I didn't find one. The 6 speed is only rated for 3500 lbs. towing, while the 5 speed automatic is rated at 5,000 lbs. I understand that the problem is that the clutch won't handle heavy loads. In fact if you check the older threads on the 2nd gen you will find that a lot of clutches have had to be replaced.

You should be able to add the tow package as a dealer option for around $500. I don't know if this includes the transmission cooler which came with my off road automatic.

I am currently towing a 21' camp trailer. The only issues is gas mileage. In the mountains it gets as low as 8 mpg. The highest I have ever gotten was 13.4 and that was with a tail wind. This can be an issues when you only have a 21 gallon tank. You need to plan ahead so you don't run out of gas on a long trip.