I had to replace the heater core in my 04 Dakota quad cab. I just laid it back on the seat and had just barely enough room to get the heater box out over the top of it and out the passenger side door. 2 things I would recommend would be change both the evaporator core and the heater core while you are in there, and to set the heat/AC controls at a certain place of your choosing and then take pics of all of the electric servos before taking the box apart to fix it. The heater hose tubes that go into the heater core are about the dumbest design I've ever seen! Good luck with it. To me, the hardest part was getting the thing unbolted on the engine compartment side.