Thinking about a change of username but worried about the work required if it doesn't auto change everything

You are just an ID number in the database. That ID number has a name. But that name can be changed. So everything is tied to that ID number, and you can safely change your name and your name on this site will change everything. Except forum posts where you and others typed your name in the message itself. (Not the name above your picture, that'll change with).

tl;dr Everything will change with that name change