Complicted rename & move files

I'm trying to create a VBS script to do the following.

Copy PDF pages from CDROM to a temp location on local machine.
Rename the first two characters from what ever they may be to WR.
List all of the colour pages. (P = Colour M = Mono)
Show how many pages in total in publictaion.
Move pages to a UNC path.
Eject CDRom
Say the Job is complete.

Example file names
BM1AA080506M002.pdf (Mono Page)
BM1AA080506P001.pdf (Colour Page)

The BM tends to very a lot but needs to be renamed to WR.

As you can tell I’m not really a programmer. Here is what I have come up with so far.
All help gratefully received.

Please could you comment any work so I can learn and understand how it all works.

Many thanks in advance

'###########################################
'
'      NAME: PageImport.vbs
'
'      Date: 17/05/06
'
'##########################################

'Copies All PDF's From CD To Temp Loaction
Const OverwriteExisting = True
Set objFSO = CreateObject("Scripting.FileSystemObject")
    objFSO.CopyFile "E:\*.pdf" , "D:\PDFTemp\" , OverwriteExisting

'Lists All Files In Temp Loaction
strComputer = "."
Set objWMIService = GetObject("winmgmts:" _
    & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
Set colFiles = objWMIService. _
    ExecQuery("Select * from CIM_DataFile where Path = '\\PDFTemp\\'")
For Each objFile in colFiles
    Wscript.Echo objFile.Name
Next

'Moves renamed Files into CTP System
Set objFSO = CreateObject("Scripting.FileSystemObject")
    objFSO.MoveFile "D:\PDFTemp\*.pdf" , "\\ms-wr-sysnas\Temp\"

'Eject CD ROM Drive
Const CDROM = 4
For Each d in CreateObject("Scripting.FileSystemObject").Drives
  If d.DriveType = CDROM Then
    Eject d.DriveLetter & ":\"
  End If
Next

Sub Eject(CDROM)
  Dim ssfDrives
  ssfDrives = 17
  CreateObject("Shell.Application")_
    .Namespace(ssfDrives).ParseName(CDROM).InvokeVerb("E&ject")
End Sub

WScript.Echo "Page Import & Rename Finished."

Wscript.quit