How does Gödel try to show that God’s existence is possible? He argues that it is possible because God has only positive properties. If God were to have both positive and negative properties simultaneously it would seem impossible for him to exist because they would contradict each other. For example, it would seem impossible for God to exist if he were to have the property of being all knowing (a positive property) and the property of being ignorant (a negative property) simultaneously. Therefore God, as the greatest possible being, has only positive properties, such as the properties of being all knowing, all powerful and morally perfect, which, according to Gödel, do not contradict each other.
Needull in a haystack 
I’ve got brain ache!
All that would show is that the proposition “God exists” is either necessarily true or necessarily false. It doesn’t tell us anything about our epistemic situation. So, while God’s existence is either necessary or impossible, (if we define God as a necessary Being) that doesn’t mean one’s confidence level is either 100% or 0% in relation to the claim “God exists”.
I find the incompatibility arguments against God’s existence to be more plausible than the ontological argument, but I still don’t buy any of the arguments.