You have to implement Password Synchronization (from AD to SAP), when a user change the password in AD FIM changes SAP Password with the same password as AD.
You can import AD Users to metaverse (Projection), Then you have to implement, at least, a Full Import and JOIN SAP Users with objects in Metaverse. After that you have to configure password synchronization with PCNS (more Information:
http://social.technet.microsoft.com/wiki/contents/articles/2762.pcns-password-synchronization-resource-wiki.aspx )
Good Luck.
PS: "Officially" SAP Web Service Connector is only for SAP HCM (Human resources, schema object type employee), not for SAP Users, but in SAP HCM has no sense password management, password Management is for SAP Users.