my (perhaps limited) experience with vehicle rust is that it is rarely confined to the place that you can originally see it first of all! However , if it is simply surface rust - which I hope it is - it shouldn't be that hard to control. I read a book called "Car Body Repairs" by a Donald Wait, published by Gregory's Automotive Publications (repair manual No. 401) which taugh me a lot about this topic. As for a hard answer to your question, I dont know to much about cots involved, and i imagine that they will vary wildly from place to place. I'd ask to see some of their previous work and or speak to previous customers if you can. thats my two bob worth - good luck!