I owned a early 2004 with a Cummins. I liked the truck but it doesn’t really apply to the truck you are looking at. They have improved them so much. I always here people that don’t own one say the Cummins is great but the Dodge not so much. Don’t buy into that. Once you drive it you’ll know if you like it or not.
Known problems? It a modern diesel, emmisions problems can be an issue be it a pickup, over the road truck or tractor. With the Cummins being no worse or maybe better than anything else. One warning, look at the payload sticker and make sure it meets your needs. I can’t remenber the exact numbers but some Ford half tons have as much payload as a 3/4 ton.