I'd get an estimate from the dealership or an auto body store. Also, if your spoiler came w/lil holes or a stamp on it, they can fill the holes or sand off the stamp so it's nice and clean. I had my dealership install my spoiler ........no worries!
I think the dealership would be glad to do the work for a nominal fee. Cheap insurance of getting it done correctly. If you try and do the work, and mess it up, you will be kicking yourself all the way to the body shop to fix your OOPS! :bill: The repair of the OOPS won't have a nominal fee either! :shock: