Charging but wont power up

My tablet is charging but the problem is it wont turn on when I press the power button. One time it powered up, I tried to use the internet but it shut down and reset. It hasn't worked since. I had it checked at an authorized Samsung service center, but they said they had to replace the main board and the parts needed are no longer have available in our country.

Would you still advise that I buy the parts and have it repaired, or should I consider selling my tablets spare parts?