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On the very bottom of the reservoir there is one more fastener. At the very bottom of the reservoir there is a single 10mm nut on a stud that attaches the reservoir. This will be somewhat hard to see unless you know where to look, using a flashlight or drop light will help. The nut faces rearward. Using a deep well 10mm socket and a 6" extension, come in from the back side over top of the coil with the socket facing forward and slide it onto the nut once you find it. Once you're on the nut just loosen it a few turns. The bottom of the reservoir is slotted, and once the nut is loosened a couple turns then you can pull the reservoir straight up and off the stud.
Replacing the coil isn't hard and you should be fine. Once the reservoir is out of the way you will remove the plug wires, the coil electrical connector, and then remove the nuts that hold the coil. If you have Mopar plug wires on the van they will already be marked for which cylinder they are, but if they aren't it's still not a big deal. The coil is marked for each cylinder. The cylinders facing the firewall are 1, 3, and 5, the front bank is 2, 4, and 6.
It's always a good idea to use a little silicone dielectric grease on the inside of the plug wire boots. You can pick up a small packet or tube of this at a parts store for a couple dollars. Just a little smeared inside the boots will keep moisture from entering the connection and corroding the coil terminal and plug wire terminal.