You can use something like this as the custom calculation script of "packageContents":
var selectedPackage = this.getField("Packages").value;
if (selectedPackage=="Package A") event.value = "3 Hours of Photography\nFamily Portrait Print\n(5) 8x10 Prints\nCD of all Images Taken";
else if (selectedPackage=="Package B") event.value = "Some text for package B";
else if (selectedPackage=="Package C") event.value = "Some text for package C"; // etc.
else event.value = "";
Make sure you set the drop-down's option to commit the selected value immediately to have the text field's value update as soon as a selection is made.
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