I'm just surprised the entire system wasn't torn down, checked, bathed, and left to dry for at least a week. Heck, even place it close to a CaCl2 dehumidifier to really make sure it is dry before use. Buying another GPU when it is very possible another component of the system is damage, could very well mean another GPU will fry. It's like replacing a head gasket on a motor without finding out what the original cause was; you can replace it, but it'll most likely blow again.
EDIT: Well, we know the original cause, but you need to diagnose the problem further to rule out everything else...