How to repair sim card tray?

Hi,

This link shows that the SIM card tray is a plug in module. Depending on what particular model Galaxy S3 you have will depend on which particular module you need, (there are 5 listed).

http://www.etradesupply.com/catalogsearc...

If you look on You Tube and search for Samsung Galaxy S3 (your model number) "teardown" or "screen replacement", hopefully you will find a video on how to open your phone and once open you should have access to the SIM card tray, which you can then replace.

Hopefully this is of some help.