Change AD Username and MS365 + resync emails

I have a user that has a composed name "Jean-Simon" that is also his Username. The Hyphen in is username and profile path is causing some issus in a particular application.

I thought about renaming his AD account to somthing like : "jssmith" to eliminate this issus but I know the AD sync with Office365 won't follow and I wouldn't want him to loose his mailbox.

I saw a powershell command but I'm not familiar enough to use it blindly

set-msoluserprincipalname-newuserprincipalnamejean-simon.smith@emailaddress.com-userprincipalnamejssmith@emailaddress.com.

Any insights on how to do this safely ?

Thank

Jeffrey