Hello Brandon,
You can easily swap the Microsoft account associated with your Windows user profile, however, you might notice some apps you have to pay again, this is typically for those apps you already paid for using the old Microsoft account, they don't transfer and merge to the new Microsoft account.
Files should be fine as long as these files are stored locally, but if they are in OneDrive with the old Microsoft account, you do have to download them from the old Microsoft account first.
This is how you relink:
Go to Settings > Accounts > Your info
Click on Sign in with local user instead. follow the steps and finish the rest.
(If you don't see the "sign in with a local account instead option, click on "Stop signing into Microsoft apps automatically" first, then relaunch this page. )
Restart the computer (Do Not skip)
Go to Settings > Accounts > Your info
Click on Sign in with Microsoft account instead. follow the steps and finish the rest. use the new Microsoft account.
Restart the computer (Do Not skip)