How much of kickboxing involves cardio and does it take long to get into condition(shape)?

I have my first kickboxing lesson today and am kind of anxious. I may not be the most fit but I do work out and play sports when I have time. I hear kickboxing is much more intense and requires a lot more cardio and strong CORE muscles. I was wondering how long it would take to get in the right shape for it. I am already aware that weight loss should come with it which is a plus. Any suggestions would be much appreciated