All the asterisks are where the GPS data would go, if the GPS was getting data to the Arduino. That there are nothing but asterisks suggests that this is not the case.
It runs on a 3.3V connection, with the ttl interface operating at 2.8V.
The 2.8 is probably not high enough to trigger a HIGH on the Arduino, which requires 0.6 * the operating voltage (typically 5.0V).
Perhaps you need a 3.3V Arduino (or a Netduino, since they operate at 3.3V).