Switching email from hotmail to @me.com

so my hotmail account which i have had for sometime has been comprimised. i have my itunes/icloud account set up as my hotmail being my primary and my icloud account (@me.com) as secondary. i want to deactivate my hotmail and move to my icloud account as primary. now i've seen some things about merging accounts and i'm a bit confused. what would happen if i deleted my hotmail account? how does apple know if it has been deleted or not? why can i not use my icloud account as primary?

sorry if its a repost.