You have a good foundation cooking on those grills. The transition to the KK won't be that dramatic. You already understand the basic principles of airflow = temperature. You will just have to get used to the new top vent settings for specific temps (bottom vent is not critical as long as the fuel is getting enough air.) The other thing will be that the KK takes quite a bit longer to heat soak, but is much more stable than those grills once up and going.
First cook should be something in your wheelhouse that you've done a lot of - pork butts, ribs, spatchcocked chicken, whatever it might be. Wouldn't recommend a packer cut brisket as your first cook!