First off, as long as you are going to a good reputable shop you don't have anything to worry about. The first thing they will do is give you a waiver to sign and a paper to declare that it is mechanically sound and has oil, blah blah blah. It will ask you everything about the engine and fuel system. There should also be a place to write any issues your are having like surging idles, cutting out, stalling, etc. If not make sure and tell them. Then they will give it a once over. Then strap it to the dyno, attach all necassary equipment (data logger, monitors, chip, etc) and set the timing to base. They won't just go hammering wot on it. They will see how the car is responding and adjust accordingly. Trust me they don't want to blow your car up no more than you want them to. That doesn't make repeat business or bring in new business.