i am in the same situation. but to be honest, don't count on doing everything in clear VBS. i had to give up in some operations, like changing site name or even creating sites! (http://forums.iis.net/t/1150762.aspx). i think microsoft didn't give us a good WMI provider for IIS7...
you will probably also find out a good way of calling appcmd.exe from VB script...
i solved it in this way:
...
sSiteName = "old name"
sSiteNewName = "new name"
If Not ShellExec("c:\windows\system32\inetsrv\appcmd.exe set site """ & sSiteName & """ /name:""" & sSiteNewName & """" ) = 0 Then
...
...
Set oWshShell = CreateObject("WScript.Shell")
...
' ShellExec
' *********************************************************
Function ShellExec(ByVal sCmd)
Dim oExec
Set oExec = oWshShell.Exec(sCmd)
Do While oExec.Status = 0
WScript.Sleep 100
Loop
ShellExec = oExec.ExitCode
End Function
....
good luck :-)