Usually the distressed ship is right near you when you first go in with a flashing beacon near it. Don't use full impulse to find the first ship or you will fly past it and loose your "path". Once you find the first ship you can use your scanner to find the rest of the ships you will be asked to find, with 2-3 anomolies thrown in.
The ship will be a dark, cylindrical shape like a frieghter looking thing so keep an eye out for it. Also use your map to help locate the area to search in. You may need to zoom in and out a bit to see the circled area on the map. It's a little bugged at the moment since the last patch.
Yes these exlporation missions are worth doing. After completing the 3/3 short missions you get 75 badges which can be used to buy green weapons, consoles and deflector dishes or blue engines and shields from the merchants upstairs at the shipyard saving you loads of money.
You can also buy green and blue ground equipment from merchants in the center, circular area of earth spacedock to outfit you and your BOs. Plus you get decent exp for doing them as well, not to mention the level apropriate drops. The missions are fairly quick and easy to complete so you can almost comepletly equip your ship and crew without spending any money.