There are a few guides around the net for doing it, but you might want to consider just paying a local computer shop to do it.
You might also want to email Pro-Star.
http://pro-star.com/They repasted the cpu+gpu on my 750JX when I got it ... still running cool and smooth 2 years later, with heavy video editing + gaming use the entire time.
Not sure if they normally offer this as a service, but its worth asking.
ASUS G750JX-TB71
- CPU: i7-4700HQ @ 2.40 GHz.
- Graphics: GeForce GTX 770M 3 GB GDDR5 RAM
- Screen: 17.3' Full HD Matte Screen @ 100Hz
- Memory: 16GB DDR3 1600 MHz. RAM 2x8
- Storage: 500GB SSD 850 EVO + 750GB HDD @ 7200rpm
- OS: Windows 7 HP (x64)
- TC: IC Diamond Thermal Compound - CPU + GPU