Dodge has a few minor issues, but nothing like the 2003 powerstrokes. You can find a 2000-2002 used Dodge quad cab for a reasonable price. The Cummins is a fine engine that will far outlast the truck.
The main issues for the Dodge are a weak electric fuel pump and the track bar. The injection pump on the Cummins uses fuel as lubriction and cooling, so if the fuel pump pressure is not monitored, it could result in an expensive lesson. Injection pumps go for $850 - $2000 depending on where you get one. The track bar is weak and makes the steering loose eventually. Easy to fix and not that expensive.
If you want to look at more information about the Dodge/Cummins go to http://www.turbodieselregister.com/
and see what people are saying and doing with their trucks.
Personally, I get 18 in town, 21 on long trips, unless I go over 70 mph. Mileage for speeds 70 and up drops like a rock.
The only things that have gone wrong with my truck are the fuel pump (from low fuel pressure), a crankshaft position sensor, and I need to put new seals in the vacuum pump.