Earpiece with no audio... Board problem

Hello,

First off, does the front camera and/or proximity sensor work? those are also on the same cable at the ear piece. To test the proximity sensor would be to make a call and put your hand over the spot right above the ear piece. If the screen goes black then it works if it doesnt then there is something wrong with that cable. Another thing ive seen if is the phone thinks there are head phones plugged in it wont use the ear piece. That can be checked buy turning the volume up and down. When the pop up for the volume level comes itll say if head phones are plugged in or not. If it does then you would try cleaning the headphone jack, or you might have to replace that cable instead. The ear piece or headphone jack cable are very easy to do.

Here is the guide to replace the earpiece...

iPhone 5 のイヤホンスピーカーの交換

Here is the guide to replace the headphone jack

iPhone 5のLightningコネクターとヘッドホンジャックの交換

To answer you other questions, yes you could replace the board, but that is close to the same cost as another phone. You would lose all your data as well unless you did icloud for a backup and restore. I would suggest checking everything else out first before considering replacing the board.