I guess you have to remove the condensation from inside the headlight. The lens is glued on so you'll have to use a heatgun to melt the glue or throw it in the oven if you dont have a heat gun.

You could buy a buffing ball and use to clean the inside with that.

You should then reseal the healight using silicone, at the edges where the lens meets the housing. And change the gaskets, I guess.

Now for the oxydation on the outside, you can use either an orbital buffer with rubbing compound or start with 1500 grit sandpaper by hand, wetsanding it and keep going up to 2000 grit, then finish off with rubbing compound with a cloth. That's how I did mine. However, the wetsanding method is killer pain, because it takes a lot of buffing. Good luck.