Not sure what site you have been looking at but I have sold all mine through ebay - http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270600262983&ssPageName=STRK:MESELX:IT is one of the listings. My website shop hasn't got them at the moment.
It will certainly prevent scratches, yes. And as Afroman (above) ays, the bumper 'strip' is pre-cut with all the holes in - just need to line it up at the bottom of the phone right up to the dock aperture and continue round past the sim holder - it all lines up.
Don't suppose you've got the 3M Di-Noc in any of the other colours have you? The silver or white patterns would look ace I reckon!