Aloha DeniseH,
Good question.
This isn't like a standard Level III or IV class of Chunyi's - you'll have the opportunity to ask questions at all levels. He will be reviewing Level I on Day one, and Level II on day two, so we'd like people to be familiar with those two classes/home study courses. He'll fill in the gaps for you, but won't teach the entire course on those days.
Your situation is a perfect reason to attend the retreat. It's set up to give you 6-days (well, more like 5, as we get into that part on day two) of practicing detection and the healing steps on you fellow participants.
You'll have the Guest Instructors there - Chunyi's advanced students, to answer questions and give assistance in things like detecting. They are there for you, so use their expertise, and come out of the retreat a confident detector and healer.
We've had people who glanced at the Level I and II courses on the plane ride to the retreat, and gained a lot from participating. The retreat is so much more than just information (ask all the returnees each year). We put the Level I and II prerequisite in place so you can hit the ground running at the retreat, rather than possibility being overwhelmed if it would be the first time you've worked with Spring Forest Qigong.
Looking forward to seeing you at the retreat,
Shawn