Difficult to say in detail without writing war and peace really but in principal the modification is not that difficult.
I used the front indicators from the 04/05 ZX10R but the mod would be more easily done with 06/07's due to the orientation of the mounting points. The hardest part is cutting the wedge out of the fairing, to get both sides symetrical and not to remove too much plastic so the indicators fit snugly with no big gaps. The key here is to remove a small amount of plastic at a time, then test fit, then remove some more, then test fit, etc etc. Once one side is done the second side is a bit easier as you can use the first as a guide.
Once the wedges have been cut out I need to make some mounting points for the new indicators to screw to. This was simply done by glueing small blocks of styrene plastic (the type used in model aeroplanes) in the appropriate areas inside the fairing. The glue was something called polyweld, available on ebay and works well on abs plastic as it melts the surface allowing other styrene or abs plastics to be 'fused' to it.
The final stage was to extend the wires from the indicators to reach the shroud under the screen where the connectors are located. This was just a case of soldering longer pieces of wire onto the existing ones and then re-attaching the block connectors to the end. Dont forget to insulate the soldered areas afterwards though.