oh, and the d50 does have an internal af motor. but you're right, the d40 does not. even then, all new nikon lenses have af motors built into the lens at reasonable prices, so unless you have old nikon lenses the d40 is still worth a look.
um, i don't think rubbing alcohol and cotton balls would do anything. you need a paint polish. try looking for meguiars scratch-x or mothers power polish and foam applicator pads at a local auto supply store.