After receiving your NES, the first thing you want to do is clean the case. I was lucky that my case was very clean and hadn’t yellowed. After cleaning your case you will want to strip everything out of it. Turn your NES upside down and remove the 6 screws. Now you will be able to take the top off the NES off. Next thing you will want to do is remove every screws you can see and take everything out of the case. This includes the power button and controller ports.
The motherboard is no longer needed.