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
No, you can't change the key pair for an instance using AWS management console. The only way to change the key is explained here: Change key pair for ec2 instance
In a nutshell, SSH key is a file, created in the EC2 instance by AWS during setup. Once the file is there, AWS is not touching it. It's only you who can work with it.