Died a week after battery replacement!

The iPhone in question was previously water damaged around a year ago. It survived after leaving it to dry for over a week and switching it off immediately after contact.

The original battery became unpredictable and would drain quickly without frequent use. As a last resort I swapped the battery for an 'official' one from Replace Base.co.uk. For a week or so it was behaving as it should and battery usage was back to normal.

The iPhone appears to have finally died a death after being used in the car on charge whilst using a sat nav app. This was about a week after the new battery was fitted - coincidence?

I've tried leaving it on charge overnight which didn't do anything, although it was warm indicating something was happening? I've also tried replacing the battery with another iPhone 5's but this didn't seem to help either!

I've since but a replacement but as I'm stubborn I would like to try and bring her back to life. Any tips on where to start?

I've managed to get hold of said device. Upon tearing it down I noticed damage on the main board - it's next to the top left corner of the SIM slot. Worth sending for repair work? It's too intricate for me.