You are going to be hard to find a shop to give you a price on installing a used supercharger kit. And if they do it may not be 100% accurate. Not because they are trying to shaft you but because they are never sure what they are getting into. If you are supplying all the parts they have no way of knowing that everything supplied are the proper piece for your make and model, things won't be as organized as they would be in a new kit, and things never go back together the same. I would find a shop you trust to do good work, and do it as cheaply as possible. And understand they may not be able to give a price up front.