Yes, the service account can be changed, but there are some insights to be aware of.
Will this affect my existing workspaces?
This question's answer depends on the configuration applied in Admin > Settings > App Settings > 0ffice 365 Groups.
If 'Use service account for Group Operations' is set to No the service account is only used when required and is applied temporarily. The account can be changed without any effect on the existing workspaces.
If 'Use service account for Group Operations' is set to Yes the service account will be added as a Group owner and member on all workspaces. When the service account is changed the new service account will have no permission on the existing workspaces causing actions to fail. In these cases you will need to add the new service account to the workspace grant adequate permission.
If the Group permissions are not updated on the workspaces, the error below will be displayed. If you have requests held in the Job Queue, these will also need to be updated with the new account before replaying.
Exception (failure) -> Error running process. Code: Authorization_RequestDenied Message: Insufficient privileges to complete the operation.
Change the Service Account
Go to Admin > Settings > Service Accounts to delete this existing service account
Add the new account and authenticate to store the token.