So, I just got the quest for Innocence Lost where I have to kill the orphanage owner, but I realized that I actually killed her by accident earlier. So she didn't respawn, which pretty much makes the quest impossible to do, so I was wondering if there's anything I could do about this, or if anyone had the same problem, or if I just cannot join the Dark Brotherhood because of this (I'm pretty sure it's the gateway quest for the Dark Brotherhood).

As it turns out, you can just tell the kid who gives you the quest that you already killed her. Sooooo, yeah, no big deal.....