I have seen the both the gsr and si lights, I cannot say offhand is the size is exactly the same, but does look similar. The SI light has a switch that allows you to turn both lights off and on, while the gsr light has push buttons for each individual side. Yes, if you remove the headliner (which I suggest doing first to test fit) you will see the two holes already predrilled there. You will just need to verify the positioning of the holes so that is lines up with the headliner.

The wires will not be seen because of the headliner, but it is only going to be one wire because the light will ground itself once you place the screw in. I ran the wire from the maplight to the driver side and spliced into a existing power source, I believe it was the dome light power source, if not you can always run it off the another power source cause once you remove the pillar, which you will need to anyway to get the headliner down, you will see all the wiring for the antenna and domelight there on the left pillar.

EDIT: I had a EX so it was a bit easier when it came to the headliner cause with only 1/4 of it removed I could easily work through the area where the sunroof begins.

Just found this:

http://www.honda-tech.com/zerothread?id=419845