Instant? Not likely, companies will not give you top end tech knowledge if you don't give them top end profits. Mid end shops are your best bet. Smaller shops are fly by night, bigger shops rely on bigger profits, mid end shops rely on customer service to make money.
Although I have never asked questions of a technical nature, PCB train have been superb - any problems with the gerber files they have rang or emailed me straight away. Sure electronics has also been equally superb.
Some places charge by the hour for any alterations needed prior to manufacture. That said, you are not going to find a PCB house which will guide you through the design process, it is assumed to be prior knowledge