My hair color faded; when i re-dye it, should I treat it as a full-head application or a touch up?

[ilessthan3you]

I dyed my hair about 2 months ago(my hair grows slowly) a medium/dark auburnish brown color. Since then, it's faded to a light brown with a ginger tint. The color isn't bad, but I liked the first one better.

Should I touch up only the roots like it says on the box, or dye over all of my hair so it turns dark again? Should I put the dye on the already-dyed parts for a shorter amount of time?

Also, I'm planning on dying it tonight, but last night I had a competition and had a crapload of hairspray in my hair, got home at midnight, and just fell asleep. So I still need to wash that out. Should I just rinse the hairspray out, dry it, then dye it, or should I just shampoo/condition it, dry, and dye?

Thanks!