The wireless card has failed in a laptop. What do you do first before you disassemble the laptop?

Make sure the laptop is turned off amd work on a anti static environment

Power it down, remove the battery, then begin disassembly of the laptop by removing all screws on the bottom, once you get access to the motherboard, remove the wireless card and install a new one. Then, screw the card back down, install the bottom cover, install the battery, and turn the machine on.