Hi, and welcome to the forum.
I've been to several of Tom's seminars but not one of the retreats. I have been to a week long program at The Monroe Institute.
It would probably be very helpful to work on meditating before you go. Sit somewhere comfortable, close your eyes, and relax. Stop your internal dialog. Try repeating a word ending in 'ing' if you cannot do it - like sha-ring, na-ring. Even if you can only do it for a few seconds at first that is alright. Any thoughts that come to you just let them drift off. If you can, do this morning and night even if it is only for 10 minutes. You should be able to lengthen the time that you sit without any internal dialog. You may even get to the point where you can drift in a sea of black without any feeling of your body or external environment. This is called the Void.
You may have a lot of things happen when you are trying to learn to meditate. It is common to have itches, restlessness, hear sounds, feel strange. You may see colors and shapes. Scratch the itch, and do whatever to satisfy your body's needs and then go back to meditating. It isn't really hard but takes some persistence.
As for the retreat, go with no fear and no expectations. Just take things as they come and enjoy yourself. I dare say it will be an experience like no other you have ever had in the way of joy, companionship, fellowship, and learning.