Back glass repair

Reportedly some of the better and more equipped 3rd party repair sites have a device that will let them replace just the back glass (Apple replaces the entire iPhone with a service replacement unit). You could call some repair sites in your area and ask if they can do such a repair and what the price is. If you do go this route Apple may refuse to provide any support for your iPhone in the future.

Not if it was broken by accident. If you purchased AppleCare + you can use one of your 2 damage incidents and pay the deductible.