overvoltage issue(is the arduino board also damaged?)

I'm using win-xp,arduino uno R3, and it was working ok, until I ,by mistake, applied a 12v on the 5 v pin (for only a second maybe) now I can't upload sketches, it says:

avrdude: stk500_getsync(): not in sync: resp=0x00

notes: -now when I press reset button the led doesn't blink like before(it's always on). -green led is also on. -my pc still recognize the ardunio(arduino com6...)but only when I remove the atmega328. -the 5v pin and 3.3 v pin, both don't give the voltage they supposed to,I removed the atmega328 and measure the voltage out of them and both give around 3v(3.09 exactly). my guess : atmega328 is damaged. so,what if i buy a new one, would it work or there might be other problems like crystal damage or any other components on the board?should i consider buying a new arduino board?

It is hard to tell what else could be damaged. Not the crystal, but for example a logic chip or capacitor, or only 1 single pin of the atmega for the USB.

You better buy a new one.

Perhaps you could try to buy a ATmega328p. You have to set the bootloader into it. If it works (I doubt it), the board is no longer reliable anyway.

ok, thanks for the reply