Layer blending

I wonder if there is a easy way in Photoshop 6 to blend two layers. What I mean is: I have two layers top one (with picture of a car) and bottom layer with picture of, let say, sky.

I want to have left side of a car very opaque (opacity 100%) and the right side transparent (opacity 0%) revealing the sky layer.

I know how to do it with gradient layer where one side I set to transparent, but how to do it with layer that contain picture?

Thanks for help,

demOkryt

Use Layer Masking. Layer > Add Layer Mask > Reveal All
Use the gradient (white/black) for the masking and you're off.

Btw, don't cross post. Most of us read all the forums here.