I've had delete-regret before and I was glad there was a intermediate step. Each item in the trashcan will be permanently deleted 48 hours after being placed in the trashcan and you can clear out the entire trashcan all at once whenever you want with the yellow button.
As to the question in the head-post, when you say, "erase", do you mean format? If so, I know of no way to format the hard drive from the UI. I would imagine that you have to get into the Service Menu to do that.