I've got a 2001 245hp 6 speed 4x4 with 240000Km on it.
Overall it is a very good truck. As said, if the lift pump is still an original style (on the engine block) it will fail (if it hasn't already) and should be replaced with an aftermarket such as FASS or AirDog. The truck will still run with a failed lift pump, but it will destroy the injection pump due to lack of lubrication(expensive!).
The sure grip diff (if equipped) is a weak point as well. Mine is completely worn and makes some noise. Eaton has a Truetrac available for it.
Cracked dash is another expensive fix, and they all seem to break.
The turbo wastegate may seize and cause overboost defuelling (loss of power) if the truck is from the snowbelt.
Aluminum wheels are known to crack around the inner bead(as mine did).
Rusty door bottoms are very common.
Other than expensive regular maintenance, and the odd wheel bearing and U-joint, mine has been very reliable and tows great.
Dave