'''Do not remove the heat-sinkproceed with this guide and fan from the motherboardunless you are prepared to clean removeand re-apply tthe hermal compound. For more information, please refer to the [https://www.ifixit.com/Guide/How+to+Clean+and+Apply+Thermal+Compound/100789|How to Clean and Apply Thermal Compound] guide.'''
Conclusion
You can follow the steps in reverse to reassemble your device, but you should not do sore-seat the heat sink and fan without cleaning and re-applying the thermal compound.