I have seen several questions and answers about changing the EC2 key pair for a running instance. However I am a complete AWS newbie at this point and I can easily stop the
I agree with @yegor256 on the best method here to change your keys. You can also visually inspect the authorized_keys file to ensure that only the correct keys are listed--especially when using someone else's AMI. Just be sure the file has the correct permissions or you could lock yourself out accidentally.