You can get rid of the yellowing by soaking the shell of the NES is dilute hydrogen peroxide and shining UV lights on the shell. There’s a bunch of tutorials all around.
I think so. After some quick googling, it looks like some people get it to work on white, grey, and blue bricks, but leaving it in too long causes white “chalky” spots to form. Try at your own risk I guess
Personally, I would leave it, but if the yellowing bothers you, I believe the procedure is to use the same chemicals beauticians use to bleach hair. You can buy kits with peroxide and a developer, you just have to be careful when applying it, and don’t leave it on too long.
“Oh! It looks like this yellowed NES is actually a rare sub-model. I forgot to get my tri-wing screwdriver bit from the car, so fuck it, where’s the drill!?!?!
Wanna buy a Commander X16? No really, I have a TON of these things.”
The thing to keep in mind if you go the peroxide/retrobrite route is that it makes the plastic physically more brittle and weaker in order to obtain the original coloring and the shell will yellow again at an accelerated rate unless you also coat it in something UV protective which will likely end up looking shiny or slightly off. I say just keep it as is and enjoy playing it while it still works.
Given how easy the front loader NES is to take apart and the simplicity of its shape, rather than Retrobrite it I would probably be more inclined to just separate the yellowed parts from the remainder and paint them.
But then, you’re also talking to somebody whose OG NES has an emerald green power light and you don’t need to press cartridges down in it to play them anymore. So, preserving that coveted originality is not exactly in my wheelhouse anyway.
I’d personally not worry about the yellowing. I’d say clean it up to remove actual dirt and scuffs and don’t worry about the discoloration. Yellowed electronics are peak retro. Hook it up to an old yellowed CRT monitor.