Okay, my hair, currently is almost dirty blonde, naturally. However, I've been using Sun-in for about 11 months - 1 year now. I decided I want to dye my hair first, a dark brown (almost black) and then a light golden blonde color to where some of the dark brown shows. I was wondering if the Sun-in and the blonde dye might turn it the wrong color.

Sun-In is simply a hydrogen peroxide mixture. It's the same stuff that is in the "developer" of dyes.

A phrase that is often used in the industry is "Color won't lighten color", meaning that a lighter haircoloring won't lighten hair that's been dyed with a darker haircolor. If you dye your hair dark brown, a light golden blonde over it will not lighten the hair. If you dye hair dark, you have to use a color remover first (ColorFix, for example) and then re-dye it lighter.

Having said, hair bleach will lighten dark dyes -- but you still have to be careful. If you dye the hair almost black, even bleach won't get it to a light golden blonde.

What you'll have to do is "weave" the dark and the blonde. The Sun-In-treated hair won't get in the way.