Can I just ask, if I now make this new email as my "primary" username, it won't negatively affect anything that currently uses my old email? Does it simply make this the new address the one I email from and it will show my new name when people email in. I just have to use the old email to log into things until I get around to updating them?
As long as you only change the primary, everything will work as it does it - but if you use Outlook apps, will need to sign in with the new Outlook address.
DO NOT REMOVE the old address. That will delete it from your account and it cannot be added back. Only click the Make primary link. If you remove the live address, you will not receive mail sent to the live address.