PS, u shud get u're acne treated first cuz they won't do microderm if u have breakouts or active acne. I would advise u get a skin consultation done, most likely they'll do a salicylic peel on u. It works wonders for skin with active ance =) And once that's been taken care of and all u need is to lighten the marks, go for microderm.
They apply a sunsceen of spf 100 after the procedure so u can step into the sun, but avoid it as much as u can.