I'm not certain that there is no God out there somewhere. It's not the sort of thing you can be certain about; no matter what my understanding of the universe might be, one could always just claim that there is a God outside of that understanding that created it all.
I don't think there is a God, or that the idea of God should hold any importance in ones life, even if such a being did exist.
What I do know for certain is that if such a being did exist, they wouldn't care one iota which religion or religious figure a person followed; it is not possible for a whole to be partial.
I'm almost tempted to suggest that they might care whether one was a good person or not, but any image that comes to mind of the nature of God seems so utterly indistinguishable from nonexistence that even this idea seems absurd. I rather prefer to be a good person for my own sake, and for the sake of those I may help.