Yup, the 3.3/3.8 (the 3.8 is a stroked 3.3) are old fashiond push rods with timing chains. Just change the oil and regular maintanance it should last forever.
I would not use the Mobil 1 ATF, it is not approved, it just says "recomended", there is a difference. Mopar ATF+4 is only a dealer item right now (although I heard Valvoline now has their ATF+4 out).
I just did a flush @ 30,000 miles on mine since I got it used. I plan on doing a filter change around 45,000 and every 15,000 after that.
Many on allpar have the feeling that by 2004, most all of the tranny issues have been resolved, but why chance it. And I agree with the above, an aux cooler will only help (unless yours has the towing package, which is not likely with the 3.3).