Custom prefix equivalent to DirectoryEntry.Invoke?

I am updating the code that interacts with AD in our application. The current code uses the ActiveD interface. I am changing the code to use the System.DirectoryServices.AccountManagement namespace. Our application allows the user to specify a password. This is stored in AD under a user-defined parameter. I know that I can do this with a method DirectoryEntry.Invoke("put").

Does this need to be done using UserPrincipal, or do I need to call a method GetUnderlyingObjectand then a call DirectoryEntry.Invoke("put")?

Any suggestions / comments would be appreciated.