I use
The Gimp so I can't give you PS CS3 specific instructions (although others could). How far have you got with masks? All you really need to know is that black is transparent, white is opaque and grey is in between; I created a mask and then used the gradient fill tool to create an effect that goes from fully transparent to fully opaque through a series of greys that make the lighter version increasingly more visible.
What I could do is another quick version, putting the final result and the mask used next to each other. Would that help?
Wulf