Dunno if you found your answer yet but here is how you could do it...
You are basically working on a 2D engine So you have X, and Y.
If Direction = 0(straight up)
X = 10
Y = 0
If Direction = 180(straight down)
X = -10
Y = 0
If Direction = 90(right)
X = 0
Y = 10
If direction = 270(left)
X = 0
Y = -10
Your bullet code could look something like
Xdir = Xdir + X
Ydir = Ydir + Y
Your toon should have its own X, Y coord. You just set Xdir/Ydir to that location(which would probably be in the middle of your toon) so you would have to add/subtract from it first to get the exact start postion correct.
This could both control the direction and speed of your bullet depending on how you code it.
Just the first thing that popped in to my head. just a basic concept of how it could work :p