I had an '02 w/ 5.9 gasser, 1500... the 2500/3500 didn't change bodies until the next year... the 5.9 magnum was available, as was the 5.7 hemi... a lot more trucks w/ cali emissions were 5.9, where most dealers elsewhere snatched up the hemi...
the 5.9 in stock form is lethargic, but a dang tank in terms of reliability. the cali emissions is actually a benefit for modding because the exhaust can be split into true duels or X/H piped with ease- as there are four o2 sensors on it= one on each banks upwind, and one on each banks downwind... the engine mother mopar should have made is easily done with this truck, boring the cylinder walls 040 and putting in 4" rods.. that displaces it from 360 to 409... a larger throttle body (52mm) and more fuel (24# injectors) and some mild tuning (recommend Shawn from Hemifever) and the torque is really really nice, along with a nice bump in HP... and still, it is as reliable an engine as has ever been made. very forgiving..
the transmission is a 46RFE, which are known to be troublesome- however, a good solenoid pack will solve any issue on an already healthy transmission.. the issue with those things isn't the trans per say, but the cooling... there is a plastic check ball in the return just behind the exchange... it likes to jam up and stop flow- and the transmission is short to live... so... remove it altogether and install a filter in it's place, and one with an anti flow back valve. poof.. problem solved. related, the transfer case have been known to argue- but a simple 'transfer case saver' ring totally fixes it..
there are many who say the 02 is the most reliable truck ever made. it is that solid... then, the 5.7 evolved, and made the 04.5 king of that moniker... they're really good half ton trucks, and can be beaten on with little concern....
my old one is for sale for $6k right now, but someone has beaten the crap out of it since I owned it, and I just don't have that kind of time or patience anymore to get it back right... now if it were $4k, I might...