I don't know about this class, Claire, however, just know that birth does not have to involve REALLY hurting. Sometimes there's no hurting at all, sometimes it is quite manageable.
My key advice is to spend the time to visualise the kind of birth you WANT to have. I visualised my calm face as the baby came down, I visualised a quiet environment with me doing 'all the work', I visualised me either singing or just humming gently. I ended up humming as I did my birth breathing (from HypnoBirthing), and everything else happened as visualised.
For many reasons, you may not have the birth you've visualised, but by making it real in your mind you are that much closer to the birth of your choice than if you don't picture what you want in your mind.
Also bear in mind that the brain does not process negatives. So, telling yourself what you DON'T want, perversely has the effect of planting the seed of the thing you don't want in your mind. To explain. If you say you don't want pain, your brain does not process the 'don't' bit, and just hears the 'pain' bit. You'll find yourself fixating on the pain factor, which is just going to create that tension, which WILL lead to some sort of pain (not maybe).
I cannot stress enough that concentrating on what you DO want is absolutely key. Even if the course of events leads to necessary interventions, you will have a far more positive experience if you can eliminate fear as much as possible.