It is doable, but will take about an hour. make sure you have isopropyl alcohol, good thermal paste and lube for the fans. Be very careful with the insane amount of ribbon cables. May I suggest iFixit tool kit as some of the factory screws are pretty snug and you will need the exact size screw driver not to strip them. I actually had to replace two of the screws because they got stripped. While doing the cleaning I also upgraded to 32GB 3200 RAM. The performance boost is definitely noticeable and the laptop runs about 5-6C cooler.

The fans on GS63 are not sealed, just 4 screws on the cover. I repasted the GPU and CPU, as well as cleaned the cooling radiators and fans, while at it I also lubed the fans. the temperatures under full load went down by 5-6 C.