How do you remove wiper arm off a 1998 windstar?

First remove the cowling by unfastening 9 screws including the ones hidden by the hood. Lift up the cover at the base of the wiper arm and undo the nut. Lift the wiper arm away from the windshield to it's fully up position and then gently rock the base forward and back and it will come loose from the drive. There is no need for a puller. The hood will probably have to be raised to about 1/2 open to get the driver's side one removed.