How do you fix a fuckup like this where some chump has taken four vertices each and put four overlapping faces in...

When I try to average normals to the faces from both sides cancel out and it basically divides by zero so the normals point every which way.

Basically I think I should delete the extra faces and then redo the normals, but I really don't want to manually select hundreds of faces, is there an easier way? The "delete overlapping faces" is useless, it doesn't find any.,