I paid $200 at my body shop to have a lip and the spoiler fitted. I'd say go to a trusted body shop, it should only be about $80. Just cos it's a dealership doesn't mean the work will be better, in fact, quite the opposite. GL, it really is a beautiful piece!
EDIT - looking at the receipt it was actually only $150 for both!! So the spoiler should only be about $60 I'd say.