Complex sentence: Starfleet has given Pressman command of the mission with orders to make sure that vital experimental technology which was aboard doesn't fall into Romulan hands, the "Enterprise" must either recover the ship's remains or destroy them.
Split into simpler sentences: Starfleet has given Pressman command of the mission with orders to make sure that vital experimental technology which was aboard doesn't fall into Romulan hands. The "Enterprise" must either recover the ship's remains or destroy them.