Thank you very much for your kind words!
Addressing your questions:
- I generally introduce Skill Checks after character creation, and I mention Sparks but don't explain them yet. Something like, "So this is how we resolve actions. Now if a task needs more than one roll to be resolved, we use these sticky notes, but we'll get to them when we need them." When I do introduce Sparks, I also explain them organically as the steps are required. "Alright, you hit them. You can draw a ray here. Now roll a d6. If you roll a 1, you defeated them! Otherwise we keep fighting." Something like that.
- If the other setting is also action/adventure-focused, I'd say the ABCs should suffice. If you'll be including world and adventure generation, I think it would be wise to revise some of the entries on the respective tables as well.
I hope you have a great time with it!