"The most aggressive of these fiduciary service marketers propose to transfer all employer fiduciary risk to themselves by the delegation of certain functions that may include plan administration, investment management or a combination thereof.... The employer is ultimately responsible for the providers they appoint to fulfill these roles and has an ongoing obligation to monitor the actions of each provider. While use of experts to fulfill these roles is often a prudent course of action for the plan fiduciary, they must always remember that their fiduciary obligation doesn't end with this appointment."