For simplicities sake, I would take a photo of the motherboard before diassambly so you know where all cables go. Mobo manual also tells you but that takes longer. Or if you have an excellent memory, memorize that stuff.
Pull all cables loose from the mobo, after that, remove all cards and memory. Be careful with the CPU. Generally, if you see anything looking like gold, don't touch it. Our hands are oily and the golden surface don't like that. It's not going to break anything but in the long run, 'goldsurface' might start oxidating. Then remove all screws and the I/O shield.
Make sure the heatsink on your CPU cooler is placed and tightened evenly so it does not rest on one edge more than others, that can kill CPUs.
Avoid static electricity.
It's not hard, just don't be in a rush, you make mistakes under pressure.