Step 1: Purchase a new Atmega. This is the version of the chip from digikey Atmega328P
Step 2: Carefully desolder the old processor. I found that is very easy to lift the pads in this process. If I were to try it again I’d probably try using a heat-gun.
Step 3: Solder the new proccessor onto the board. Pretty straight forward, assuming the board was not damaged.
Step 4: Program the Arduino bootloader. This can be done using another Arduino board, or a dedicated programmer. I used my USBTinyISP for the first time and it works great. It interfaces directly with the Arduino IDE and is a lot more convenient than having to wire up a spare Arduino every time.
Step 5: You’re arduino is now repaired.