Modifier a shapekeyed facial setup

Hi guys
I got this nice model called Brave by Zuendholz from Blendswap and it has a facial shapekey setup that i like.I was hoping to be able to modify the face so i could use the system for various characters but when i try in edit mode it just returns to its original form when i switch back to object mode. Is there anyway to modify this face(disable shapekeys maybe)?.

mainchar2.blend (1.08 MB)

If you select basis under shape keys it should work

Hey Kazinger i select basis and then there a bunch of names to select from which do i choose?