Short answer: You'll be fine.
No prior CS knowledge required. Teaching the CSP course is all about being the "lead learner" and jumping in with the students. Might take some getting used to if you're used to being the authoritative source in the classroom, but I've heard many teachers express much success with letting go of that idea and embracing when students ask questions you might know the answer to and responding with "Great question! I have no idea! How might we find out?" Based on the way the curriculum is designed, you basically learn with the students through exploration together. This is my 3rd(?) year teaching CSP and first year teaching CSD and I've felt very comfortable picking up the CSD curriculum because I feel its philosophy and style closely matches that of CSP.
In my opinion, it's more important to adopt the "lead learner" attitude than it is to have the CS background knowledge.
In terms of my "expertise", I've had some introductory programming experience so when I started teaching CSP, I was comfortable with the programming, but I ended up learning a lot through the CSP curriculum about how the internet works. Not many of my students knew much about the inner workings of the internet either, but I had an occasional student in the Cyber Patriots club or had some experience dabbling in computers and might add to the conversation (usually that just looked like the whole class wondering what the kid is talking about and me nodding and saying thanks).
If you ever do get stuck on a question you don't know the answer to, tell your class you'll get back to them, post your question on this forum, then share the responses with your class.