How does the Apple warrant replacement with an iPhone 5 work?

The lock button on my iPhone 5 is not working properly. Most of the time, the phone doesn't recognize when I press the button.

I plan on contacting apple to have the phone replaced under warranty.

Do they send me a replacement phone first, then I send them the defect?

I'm in the middle of a move, so I do not want to be without a phone, if avoidable.

To best of knowledge, apple has the fastest and best costumer care according to the law and regulations! However apple is not my field of research but I can, t hide the facts! They replace it in a shortest possible time if needed!