Yeah don't worry too much, the classes are nice-to-have but are not vital. You can always find a Lamaze class online and some organizations (even some libraries) offer DVDs at little to no cost. Stay calm and trust in yourself - everything is going to be alright. Good luck mommy!
You could always look then up on YouTube. But trust me once you are there your body will just know what to do. I just had my third son and I didn't take any classes with any of my pregnancies. The nurses in the hospital were like my personal lamaze instructors, they helped me through every step of the way.