What makes the guy sure its the turbo?? Usually when turbos go out, the car will smoke like a freight train.
Also, if hes saying it locked up or something, your check engine light will probably go on since the engine wont see the requested boost pressure that the ECU is asking for. VWs have a tight grip on boost pressure. It asks for a certain pressure and if it doesnt get it(verified by the pressure sensor in the intercooler tank) the ECU lets you know it.