My guess is you roasted the trans driving to your parking spot. The leak is a blown front seal which in itself has nothing to do with the slipping more than likely. Get the trans built. Also dont drive the car in the future when something bad has happened. They dont appreciate it and take it out on your wallet.
One final thing. If you dont know how to properly add the trans fluid you may still be low. Especially considering you pumped all the fluid out of it when the radiator was destroyed. Low fluid plus not clearing the code that had it in limp mode would make it behave like that. Its a slim chance but that might be all thats wrong with it. But unlikely.