you can buy just the plastic screen bit anyway, and its easy to change.
the original one is held on with double sided tape, just carefully lift it up and off.
changing the complete housing is quite tricky and easy to damage something if you havent done one before (esp the ribbon clamps)
you can get the lens on ebay for £4 delivered
item 140035676422
you will need some double sided tape to stick the new one on, available from the £1 shop