I find it difficult to believe in and trust God, I have heard all of the arguments for His existence, such as the kalam cosmological argument and others like it, so I believe that there is a real possibility that God exists. Also I am quite versed in Christian theology and believe that if God does truly exist He can only be the God of Christianity. I'm not sure why I have such a hard time believing in Christianity, but I believe it has a lot to do with the sin in my life. How can I overcome a sinful and hardened heart and truly seek after God?
People often have difficulty making truly unbiased decisions. One of the reasons bribery is wrong is because the idea of making money from one decision over another perverts the justice of the decision. "And you shall take no bribe, for a bribe blinds the discerning and perverts the words of the righteous" (Exodus 23:8).
It appears that you acknowledge that God probably does exist, but you also realize that admitting that fact means you have to make changes in your life. Thus, I would conclude that even the best argument in the world would not change the situation if you prefer continuing in your sins.
Therefore, let's address this from the other direction. I don't know what sins you have in your life, but are those sins, overall, benefiting you or harming you? My guess is that you see problems with what you are doing, which is why you are willing to admit that they are sins. If there is a better why to live life, would it not be worth while making changes. Sins tend to offer immediate gratification at the expense of long term problems. Righteous behavior gives long term benefits, but might mean giving up or delaying short term pleasures. Therefore, the question is do you live your life for the short term or the long term? "A desire accomplished is sweet to the soul, but it is an abomination to fools to depart from evil" (Proverbs 13:19).
But let me take this a step further. If you realize that some actions are righteous and others are sinful, then where did this moral judgment come from? Once someone admits there is a right and wrong, then they are acknowledging that there is a standard that exists which is above men. It isn't from men because some things are seen as right or wrong regardless of how many people disagree with the conclusion. Any standard needs an author. The logical conclusion is that God is its author.