Don't rely on it being preserved. Many repairs require Apple to replace or reformat the hard disk, which will result in the loss of your data. Please make sure you back up your data on a regular basis to minimize your data loss. Apple and its AASPs are not responsible for any damage to or loss of any applications, data, or other information stored on your MacBook Air while performing service.
Much like Apple handles support calls over the phone, soon only customers within their warranty period will be able to access online chat support through getsupport.apple.com for free. For others, Apple will charge what it refers to as a “pay per incident” fee or require the purchase of an extended warranty through AppleCare. Previously all online support chat features were available for free to users worldwide. Some users might have noticed back in August when Apple revamped its support sites that it started listing a $19.99 per incident fee for chat support. However, up until now AppleCare hasn’t actually been charging users to access the feature.