Sheared woodruff key

[MuddyArgyle]

I was struggling with a non-start issue on my 2011 ec300. I decided to look at the flywheel just to see if anything looked off. I found a piece of metal in the flywheel slot, and sure enough NO metal where there is supposed to be the woodruff key.

Is it possible to fix this without pulling the whole motor apart? Do I need to replace the whole crank? I've heard about compatibility with cr250 motor parts? Alternatively is there a way to repair it without replacing/rebuilding the whole bottom end?

In the pic, I also notice that it's really oily in there, so I guess I'm replacing the seal anyways...