Well, if you have deep cracks, no polishing will make a difference. Unless you get OEM lenses (which probably cost ridiculous amount of money) you might have issues with fitting non-OEM lenses to OEM housing. Instead, buy new set of headlights. I start with brand new set every time I retro-fit, they only about $80-90 each for a very good brand virtually identical to OEM (don't buy cheapest, I got CAPA certified and they are awesome quality).
The reason for that is retrofit is not a one-day feat, at least for me. I buy new headlights and while my old are still on the truck, I start working on my retro, it can take up to a month if you don't have all parts or wing in it with design, painting, sanding, painting some more like I did. There is no blueprint or step-by-steps on how to mount projectors/halos/etc in 4Runner housing, you will have to figure it out as you go, and it takes time if you want to get it done right. But if you working on your original OEM set, your 4Runner will not be drivable in meanwhile. Of course that may not be an issue for you, I don't know your circumstances.