A system and associated method for delivering to an internal body site a selected one of a plurality of instruments. An instrument storage chamber is providing having passages for separately accommodating a plurality of instruments. An outlet guide tube couples from the instrument storage chamber and receives a selected one of these instruments for delivery to an internal operative site. An indexing mechanism is provided associated with the chamber for causing relative displacement between the instruments and the outlet guide tube. An instrument driver displaces the registered instrument from the chamber into the outlet guide tube for delivery to the internal operative site.