The hard drive has been replaced, so there is no Recovery partition.
I don't see where he said that.
Anyway, temporarily put it back in, use recovery partition to install on the new HDD, and pull it back out.
He did say new hard drive
If the Mac came new with ML installed, you can not download it from the App Store : it is not in your "Purchases" tab.http://liondiskmaker.com/
I think as long as you have a legit copy of this registered to you on the app store you should not have a problem using this to do a clean install
I did it for my MBP that I sold in early September in anticipation for the new retina MBP
I think a purchase allows you to install mountain lion on 5 computers?