So I did this for the G75. I do not understand why it will void warranty. It's in fact extremly simple. Much simple than one might think at first sight. I was a little bit worried. There should be some void warranty stickers for important stuff (for example removing the MB itself maybe, even it's the only way to repaste. But just to change RAM and WiFi card, it should be fine. Even those ribbons snap into pace quite easy.
Asus also did a great job with the A-B-C screws marks. There is no way not to know where every single screw goes.
As a down side, there is little room to take out the fans for cleaning without removings the screen. In on laptop after only one month, there is quite a bit of dust. In my country damage done by dust over component falls outside warranty. I've said it before, there is no way to clean G55 and even with G75, a proper cleaning means taking the fans out.