Arduino pin 13 dead - does that mean replacement board is dead?
The fact that you cannot upload anything to the Arduino is a good indicator that it is dead. Unless you have the SMD version of the UNO, you can replace the ATmega328 by itself and keep the rest of board. You will need to burn the boot loader first, as LeoR pointer out.

It possible however, to fry the ATmega16u2 microcontroller (black square behind USB connector and next to the metallic crystal oscillator) that enables the ATmega328 to be reprogrammed. Since the ATmega16u2 is a surface-mount component, you cannot replace it by itself and must replace the entire Arduino UNO. One way to fry it is to connect 12V to the DC jack and connect a jumper between VIN and 5V. This will fry both the ATmega16u2 and ATmega328.