Yes, you can seperate and change the outer screen of lumia 1020,indeed if you are a DIY guy it is a little tricky. I have a lumia 1020 whose outer screen got shattered but the touch and the inner screen was still working ,I however fixed my screen that way but i eventually ended up with minor defects , its not impossible if you have patience and steady hands ,I did not find any guide on this kind of repair of 1020 but i did refer to the iphone guide (https://www.youtube.com/watch?v=z9drzO9hO_U).
You can buy the screen replacement kit at ( http://www.ebay.com/itm/Outer-Touch-Screen-Replacement-Lens-Front-Glass-Cover-Tool-for-Nokia-Lumia-1020-/360843089061?hash=item5403ec94a5:g:FOsAAMXQlgtSpVbq)
Good luck.