https://www.apple.com/support/iphone/repair/
You could save a substantial sum of money at a reputable non-affiliated repair shop. However, be forewarned of possible issues in the future. Certainly, if the work done by the non-affiliated shop causes a problem, Apple correctly will not fix it. However, there are some Apple fanatics that wildly claim that merely opening the device will cause Apple to refuse ALL future service, in or out of warranty.
Make your own decision. The following will lead you to the appropriate Apple documentation:
http://www.apple.com/support/service/
Select “iPhone”
http://support.apple.com/kb/index?page=servicefaq&geo=United_States&product=ipho ne
Select “Learn more about service coverage”
http://support.apple.com/kb/index?page=servicefaq&geo=United_States&product=ipho ne&select=WARRANTY__PRICING
Under Out-of-warranty repair service, select “Read Apple’s Repair Terms and Conditions”
http://www.apple.com/legal/sales-support/terms/repair/
Select “General Terms”
http://www.apple.com/legal/sales-support/terms/repair/
Select “English”
http://www.apple.com/legal/sales-support/terms/repair/generalservice/serviceterm sen/
Scroll down to section 1.10.6
1.10.6 Disclosure of Unauthorized Modifications. During the service ordering process, you must notify Apple of any unauthorized modifications, or any repairs or replacements not performed by Apple or an Apple Authorized Service Provider (“AASP”), that have been made to your product. Apple will not be responsible for any damage to the product that occurs during the repair process that is a result of any unauthorized modifications or repairs or replacements not performed by Apple or an AASP. If damage results, Apple will seek your authorization for any additional costs for completing service even if the product is covered by warranty or an AppleCare service plan. If you decline authorization, Apple may return your product unrepaired in the damaged condition without any responsibility.