Y'know, I don't actually get to DECIDE that. And it just so happens that I'm not. Although I've been one in the past, and I know the general mindset. I still agree with atheists on a lot of things, actually. Especially when it comes to the importance of civil rights for everyone, and the horrors of mind crippling dogma, and the many flaws and dangers of mainstream, organized religion.. So I could probably still fake atheism with relative ease. Just.. leave my own spirituality out of it, and go on raving and raging against the abuses of Christianity and Islam, etc. I could probably fool quite a lot of people that way, methinks...
Still... I think I'm maybe slightly too moral, and I've got slightly too much honesty and integrity for that, unfortunately. I don't want to have to fake it all my life. I don't want to be in the position of not getting to worship, or be involved in spiritual practice, in my own way. So.. I think I'd probably decline. Seeing as spirituality is something very important to me in my life.
As for letting you mess with my brain, to the point of changing it back to the way it once used to be, during my years of diehard atheist materialism, via drugs, or surgery, or electronic stimulation, or whatever..? Eff that too. You can keep your money. I'm a lot happier with my reality being what it is now! It used to be SO exceedingly narrow and limited, I can't even word.. And also, very grey, mundane, purposeless and hopeless.
..I just might let you reset my brain for ten million dollars if I could still mess around with it afterwards, however. Like.. take a bunch of acid, and ayahuasca, etc, with the intention of having a high-level mystical experience.. That was what changed me last time, and I'm sure it could do so again. It might even be fun, actually.. Getting to RE-experience my reality opening up in those ways. :)