Two seperate Motherboard problems for 8g.

Logic board #1: The screen stays in start up and with the apple logo and does not go pass it. It seems to freeze. It was not dropped or anything. I stopped using the phone for about a month, when I went to go use it, that freezing happened.

Logic board #2: This was purchased broken with the connector for the proximity sensor broken right above the clip. How would I go about removing and replacing this part?

Thank you very much for your time.