After I crumb coat, can I wait overnight to frost? I'm thinking that the crumb coating seals in moisture. Am I right?

Yes. I usually do and with better results than if it's just an hour or so.

Yes.. the crumbcoat will seal the moisture.. Just make sure to seal the cake well in plastic wrap so it doesnt sweat.. It would make your second layer easier to add too!
Edna

Yes, it seals in moisture and also keeps you from pulling up crumbs into your icing when you frost the cake.

I need to saran wrap after I crumb coat?????

Yes...put saran wrap so the cake doesnt sweat.. And to avoid other flavors to get into the buttercream..
Edna

Thanks... I usually do celebration cakes and am doing my first huge wedding cake... and i'm having to fit it in with my family life...lol....

Good luck with it!
Edna