ok ive dyed my hair since i was 13 and i honestly dont remember its natural shade...lol
ok.
blond to black.
using permanent black dye will result in you NEVER reaching that exact shade of blond ever again. seriously. you are permanently COLORING your hair, whether it fades or not the hair you dye will always be dark. a pro stylist can lighten it from faded black to a light brown maybe but it will fry your hair. bleach is death for hair no matter what they tell you LOL.
as for pink streaks. try something semi permanent like "iced cream" brand. it may stain your virgin hair a bit but it wont be as damaging as permanent color. yknow?
-tae