Need help on Arduino as ISP
There are more ways to flash a bootloader to new AVR chip. To which you refer? If you replace the chip on Uno to burn a bootloader to it with a programmer, then it is very unclear what you are asking, because the original chip is not involved in this process.

If you ask about ArduinoISP sketch, then simply it is a sketch. You upload it as any other sketch and replace it with any other sketch.