My LG G4 went dead

I started getting force closing issues with the camera and/or it would freeze when I started it, it would go into a reboot sequence and work for a short while. Then all of a sudden it turned off and refused to turn on again, no lights come up when charging. So I'm guessing it's a motherboard issue and I'd like to try to repair it if it's cost effective. Warranty is a no go as I bought it over eBay from a store in Korea and I live in Canada. I already bought a new phone but I would like to see if this can be repaired. Any tips on how to troubleshoot?

Thanks!