We found 4 Reddit comments about Batman: Going Sane. Here are the top ones, ranked by their Reddit score.
There actually is a story about that. Except, rather than putting on the cowl, Joker tries to settle down and live a normal life.
You can imagine how well that works out.
There's a comic about that.
That and there is other textual evidence that he would at least try to give up being joker after killing batman. Going Sane http://www.amazon.com/Batman-Going-Sane-J-M-Dematteis/dp/1401218210
Though that story doesn't really touch on whether he meant to kill Batman or if it was a fluke.