I took my 3.0Si badges off - makes the wing look a lot cleaner, not least because there's less places for wax an polish to get stuck... But IMO it just allows the lines of the car to stand out more by smoothing the wing.
As for positioning, take photos. Then if you want them back tbh you'd be as well buying new ones off eBay for a few quid as they will have the adhesive attached. It'd pi55 me right off having to strip all the old adhesive off the badges then bugger about cutting new stuff to fit. I still have mine though, as well as a bunch of other bots I have swapped off so's I can fill up the boot for any future buyer