I had to do one on my netgear MT814v2.
READ THE INSTRUCTIONS
It wasn't that hard though.
Very similiar to a bios update. If you can update the bios you can upgrade your firmware.

Oh, the firmware update I did on mine made the world of difference. It would loose connection about every hour or less. Since I did the update I never have to touch it. It's been Rock Solid. It's the one thing I can depend on......