Yeah, Don't send your hard drive, it's not hard to forget because it's printed in big letters on the instructions not to do so. If you did you wouldn't get it back. As far as if you would get your console back, not likely. So far from the consoles I have sent in I've always gotten a new one, and by that I mean one with a new Serial Number, Manufacture Date, etc. I don't know that it's actually "new" or just refurbished, probably the latter.
It's just easier to send out a new one then to fix the old one, plus it takes longer.