I did this last night to my macbook air 11" mid 2012. I had been running at 100 to 105°C, and had up to 10 minute delays coming back from a sleep, while the CPU hit 100% with high temps. When I got into the macbook, it was pretty easy... though the parts are small. Getting to the heatsink was easier than I have found on most desktop ATX case machines. The thermal paste on the CPU was dried and cake-like. I gently removed the paste with the spudger, and it came off easily. I cleaned it up with Arctic paste remover and cleaner, and then reassembled with arctic silver 5. I used the long, rice grain - like bead of grease approach, rather than the recommended smearing technique. Right now, I have a number apps open, and am running at 60°C (vs. the mid 90°C range), and it comes back from sleep immediatly. I don't see the dreaded kernal_task, and i have loaded up the machine and it only hits about 85°. I think in general, I am running about 30°C cooler, and the machine is performing like new again.