you will only need a little but sanded out of the clock space, and you shouldn't see anything you sand as it's mostly in the back/inside and the timer covers it up. Get some 2000 grit sandpaper to finish it off, which should get rid of any scratches and the like once you've dremeled the sides. And don't use a cutting dremel tool, use a sanding one to sand the inside edges down, working from the back side to the front and test fitting the timer constantly. This should give you the look you're going for.