I see Clint has already given you a good start. I'll add my 2 cents.
You're also going to want to separate the fan from the heatsink because a lot of dust and debris get trapped there. A old toothbrush will help you get between the fins.
A couple tips for using ICD
First secure the end of the syringe to make sure it's air tight (just push it on, make sure it's tight), you don't want water leaking into the syringe. Get a small glass of hot tap water and let the tube soak in the hot water for about 3 minutes. You want to submerge about half of the syringe tip first. This will soften the ICD making it easier to get out of the tube. When you remove the syringe from the water be sure to dry it off before applying the thermal compound.
Since ICD is very thick you do not want to spread it, use the compression method to spread it or you'll end up with air bubbles.
Here's a link to proper application.
http://www.innovationcooling.com/application.htmlOther tips:
Be careful not to bend the heatisnks, most of the ROG G series laptops have heatsinks with a slight bend that go away from the motherboard. If you put the motherboard on a flat table and push, you will bend these heatsinks. It's best to elevate the motherboard with box or stack of magazines so you don't bend the heatsinks when removing them from the motherboard.
Do not pull on the heatsink if it is stuck. If you removed all the screws and it still won't budge give it a slight twist, it will help break the dry thermal compound loose. Don't twist it too much or you will damage the thermal pads on the gpu.
Whatever you do, do not use force. The laptop and all of it's parts are designed to come apart. If you're having a hard time with a particular part, look around that area for a screw. Laptop manufacturers love to hide screws everywhere. Be very careful with the zif connectors, and close them after removing the cable. If you don't close them you could break them when removing the heatsinks.
One last thing, be aware of ESD. Electrostatic Discharge (ESD) can short electrical components in the motherboard. To avoid this simply touch a metal object when you sit down in your chair to work on the laptop. If you walk across carpet sit down and touch your desk leg or desktop computer case. It's a very simple step to remember that can cost you a lot if you're not careful. There are better ways to ground yourself such as an
anti-static bracelet, but you shouldn't need one for this single repair.
I hope this isn't too overwhelming for you, if you have any questions we're here to help.
Good luck.