2004 Dodge Caravan replacing spark plugs

I'm sure you already know the front ones are easy. For the rear, do the following.

Using an 8mm socket, remove the air tube between the air filter box and throttle body and remove the air box cover and induction tube. At this point, you should be able to reach your arm behind the engine via the space you opened up.

NOTE: Based on when your 2004 was built, you may need to also remove the cowl assembly at the base of the windshield. Early 2004 vehicles may require this. To remove it, open the hood and there are aprox 4 bolts across the front of the cowl under the hood. Remove them and remove the 4 torx screws at the top of the cowl. Next, you will need to remove the wiper arms and wipers. Once they are removed, you can remove the cowl and you will have access to everything behind the engine.