Thanks for the quick response - you gave me some good tips! I wasn't able to use the crop tool for the whole solution bit it provides the selection tool...
Here is what I wound up doing:
1) Drawing the crop tool on top of the image with no fill color.
2) Adding 2 shapes on the base image, a 'mask' drawn with a semi-transparent rectangle and a selection filled with the underlying image bits. The crop tool provided the selection rectangle. These are drawn in UpdateDisplayList()
3) Adding event listeners for MOVE and SCALE on the crop item to update the selection rectangle.