You will need to remove front bumper, but you don't have to remove it completely from car just to remove the bit under headlight. You need to undo two big bolts which hold bumper in place and then pry off bumper forward from one side of the car to create just enough space to access from inner side of it to remove some screws with a ratchet or small screwdriver and then unclip the chrome strip. Clips can snap off, so I'd suggest to purchase some clips from Audi or from A8 Parts before removing that strip.
I have powder painted those trims about year ago and I'm very happy with result:
http://forum.a8parts.co.uk/showthread.php?t=4587