remove mark screws from bottom Case
Then using some plastic to pry up top case starting from right side near USB port
and moving to front and left side of laptop
after that lift up case a bit and disconnect keyboard and touchpad FFC cable
To remove screws that secures battery. Lift it and remove
disconnect speakers cable
remove screws that secures HDD, HDD board and USB board
lift HDD with boards and remove them
remove screw that secures optical drive and remove it
remove LCD cable
remove Antenna cable
And remove rest of screws the secures mainboard in the case
Now lift mainboard from right side and remove
disconnect fan cable
And remove screws
now clean all thermal paste from CPU and GPU
Clean dust in the fan near heat sink
Now apply a new thermal paste
place hit sink. Tighten screws
and connect fan cable