With baptism, so long as you're truly repentant then everything will be washed away.

Congratulations on being baptized!  I agree with the other posts.  Stay close to your missionaries and stay in daily contact if possible.  Keep reading the Book of Mormon and you will be fine.  Remember, Joseph Smith's experience was not unique - Satan always tries to prevent you right before great spiritual moments. 

Here are some excerpts from one of my favorite talks from Elder Holland (Quorum of the Twelve Apostles) discussing just this thing, "There is a lesson in the Prophet Joseph Smith's account of the First Vision that virtually everyone in this audience has had occasion to experience, or one day soon will. It is the plain and very sobering truth that before great moments, certainly before great spiritual moments, there can come adversity, opposition, and darkness. Life has some of those moments for us, and occasionally they come just as we are approaching an important decision or a significant step in our life. ...
I wish to encourage every one of you today regarding opposition that so often comes after enlightened decisions have been made, after moments of revelation and conviction have given us a peace and an assurance we thought we would never lose. ...
In LDS talk that is to say, "Sure it is tough--before you join the Church, while you are trying to join, and after you have joined." That is the way it has always been, Paul said, but don't "draw back," he warned. Don't panic and retreat. Don't lose your confidence. Don't forget how you once felt. Don't distrust the experience you had. That tenacity is what saved Moses when the adversary confronted him, and it is what will save you....
This opposition turns up almost anyplace something good has happened. ...
but once there has been genuine illumination, beware the temptation to retreat from a good thing. If it was right when you prayed about it and trusted it and lived for it, it is right now. Don't give up when the pressure mounts. You can find an apartment. You can win over your mother-in-law. You can sell your harmonica and therein fund one more meal. It's been done before. Don't give in. Certainly don't give in to that being who is bent on the destruction of your happiness. He wants everyone to be miserable like unto himself. Face your doubts. Master your fears. "Cast not away therefore your confidence." Stay the course and see the beauty of life unfold for you." (Elder Jeffrey R Holland, "Cast Not Away Therefore Your Confidence" given at BYU on 2 March 1999 http://speeches.byu.edu/?act=viewitem&id=795&tid=2)