CHANGING THE SCRATCHED LENS PLASTIC COVER
This is a very easy thing to do on these phones. So when you've scratched the plastic lens, it's simply a matter of buying one from ebay (I paid £5 inc postage for my one on ebay)

Press the centre of the screen lens cover with a reasonable amount of pressure. Get a very small screwdriver or a dress making pin. With the centre of the screen pressed, push the screwdriver gently under the corner just above the MENU button. This will lift the corner of the lens, enabling you to gently slide the screwdriver around the edges. Starting at the bottom by the menu keys and working your way upto the ear piece.

The new one can now be replaced with some double sided tape, cut into thin strips. Blow away any dust on the screen before fitting it