What to do with filler neck

I bought a used filler neck from a member here. Looks to be in pretty good shape. I will be installing this in the car when I swap out the gas tank.

Anyone know what I should do about the surface rust on the front of the filler where you put the gas in? Should I just sand/steel wool/scotch-brite that and leave it? Or should I paint it? What kind of gas/fumes resistant paint do we use on these?

What about the corrosion inside, which I showed on the back side of it? Anything that can be done about that or just leave it?