I will weigh in here as well.
My computer / device repair shop functions in this way as well. Customers drop off computers or mobile devices for repair. Say they ask for a virus removal or just a system tune up. We put that on the sales order and a tech works on the service. If in the process we discover there is no anti virus etc., we will produce a separate quote and send to the customer. If it is approved, it goes onto the sales order. When the order is completed, it gets converted to invoice and billed.
We have custom fields for status of sales orders and initial problems that help track where a project is on the work flow.
That being said, I would love a copy to sales quote from sales order.