I want to know if it can work out.
This would depend entirely on the both of you.
But could a theist and an atheist work together in a relationship? Why not? It just requires that bother parties accept their differences. If he's more interested in proving to you your God is not real and you're more interested in saving him from hell, then it's I don't think it could end well. If you're open about each other's views and are happy to talk about them maturely and respectfully, then I don't see how it would get in the way. Such couples have worked before and to be honest, if theists and atheists can be friends, why can't they be lovers. The main thing I see getting in the way is 'hell', because generally theists view us as hellbound and we're not looking to be saved, because it's disrespectful, heck I might even say insulting. But not every theist thinks that way, heck I know theists who believe that I would be welcome in heaven, so I won't pressume to know your beliefs.
And of course, we don't know what this other person is like. Some atheists, like any other type of person in the world, can be a-holes, they can be full of themselves, arrogant and annoying. The fact you're asking this question suggests that maybe he isn't that type, as hopefully those traits would be a turn off, then again, some people are attracted to that. :S I'd say atheists are a varied bunch, but I'd say if I were to date a Christian, the main thing I would hope is that they don't shove religion down my throat, I'd be much happier if we communicated on the same level, not necessarily on the level of atheism, but on common traits, on things we can appreciate and put aside our differences, because as far as everything else is concerned, they're not important to the relationship.
Anyway, welcome to the forums. I hope that you're able to come here and have a good stay. I'd say as far as atheist forums go, we can be a tough bunch, I'd say wear thick skin and unless somebody actually does make a personal attack (in which case hit 'report to moderator'), avoid taking anything personally, because even if somebody's comment is loaded with sarcasm, they're not trying to get personal. Your arguments will no doubt be scrutinised. Some theists don't like how it works here, some do. The rules & mods try to accommodate for free speech as much as possible, but obviously, if something gets out of hand, someone will likely act (if they are aware, hence 'report to moderator' button

). We're actually quite varied here in terms of who we've got in terms of atheists, different people have different approaches.
Regardless, we're not an unfriendly bunch (chatter is a good place to wind down, might be useful if you get in an intense discussion) and if there's any support you need, generally I like to think people are good at giving it.