When you've got a massive script like that, please attach it as a TXT file rather than pasting it into the forums. You can edit your post, if you like, to attach your script, or add a post to this topic with the attachment.
Also, you're going to have to be more specific. We obviously can't rewrite the script for you, and it's a bit tough to look at a giant script like that and offer any help, unless you have a specific question you'd like answered.
You can start with http://technet.microsoft.com/en-us/library/ee221101.aspx for a general conversion guide. PowerShell isn't a "scripting language," though, and simply "converting" a script isn't going to take advantage of what PowerShell is and does. It's often else work to simply start over, and you'll typically wind up with better results, too.