I accidentally connected +5v to pin d0 and it doesn't work anymore. How can I fix it by finding the damaged component or is it dead and gone?
It's probably dead and gone. Were you using D0 as an output pin?
You applied +5v to a non-5v-tolerant pin on a 3.3v microcontroller; I'm not surprised it doesn't work again. Luckily the boards are dirt cheap!