Yes. You do need to change the passwords for all accounts that have external passwords like SAS installer account , the first user account (sasdemo) ,the sas spawned server account sassrv).
Basically there is a specific SAS Deployment Manager task for updating any persisted passwords. Typically the sas install user and sasdemo are not persisted, but sassrv is. The menus will show you what passwords are relevant in your particular environment.
The SAS Users Group for Administrators (SUGA) is open to all SAS administrators and architects who install, update, manage or maintain a SAS deployment.