Do not lend account details unless you've done this.

First off, be signed in to Xbox.com. This is needed for later. Secondly, have a friend monitor your account for activity. Now, as soon as you've given your details (which you shouldn't have your normal ones), ask your friend to check for activity. When they see it, go on Xbox.com and change your email/password. As soon as the hacker logs off of the account and you log back in, you retain access. Screw off, scammers. I've learned this by experience.

Edit: Forgot to mention this, have your friend be on skype/steam so you can communicate. Not through XBL, obviously.