My Nexus 5 has water damage apparently. Can it be repaired?

I am in Brazil for the foreseeable future and have managed to break my phone... and prices are very steep here to just go buy another one!

I took it to a repair shop in a local favela... my friend knew the owner and so I could trust him with my device. When I went to pick it up he said that the 'placa' had begun to corrode due to water exposure... which I believe is something like a motherboard.

I am not sure how any water got in to the device... I have had it for about 6 months and not once have I dropped it in a puddle or taken it out in the rain etc.

It started acting strange..lagging up and resetting itself. Then it started resetting itself constantly just getting to the Google logo and then resetting again without any way to stop it.

Now, I believe the battery has just died so it is just a paper weight at the moment.

Any suggestions? Can I buy spare parts? Or should I sell for 70 reias (basically 25 dollars)?

Thanks in advance!