There are very good recommendations in here. I did record my presentations in advance for many occasions. I must warn you that it is a lot of extra work if you've never used editing software before. If I may add something: If you choose to do it live, take your time. I know it's hard and it can be embarrassing but try to remember that it's ok to stutter, it's the way we speak and people should be patient enough to hear what you have to say.