In my opinion, any type of service-related business that is run well asks the questions for you. Instead of going to some place that just sells products, try going to a nice detailing shop that will inspect, or at least ask about the condition of your car. They should want to know things like make and model (paint characteristics vary between cars), color, age, condition, previous care, garaged or not, your budget of time and money, etc.
If you don't have a local place to inspect the car for you, try calling Nick or Heather at Detailer's Paradise.
http://www.detailersparadise.com/_system/_advancedstore/qryDefault.asp