I believe you may be able to utilize the digital pins as serial connections by using the SoftwareSerial library in your sketch (https://www.arduino.cc/en/Reference/SoftwareSerial). I'm guessing you are using an Arduino board that only has one UART, so this library allows you to "pretend" that you have more UARTs and use your digital pins as TX/RX pins.
I did this recently as I was experimenting with a GPS module as well (https://www.sparkfun.com/products/13740). Using SoftwareSerial, I was able to hook the GPS to pin 3 on a Sparkfun RedBoard to listen it (this GPS module doesn't receive data, so I only had to hook it up to one data pin), and at the same time I monitored the data using the serial monitor (hardware serial through the UART).
As a side note, I used the TinyGPS++ library to help extract data from the GPS module (http://arduiniana.org/libraries/tinygpsplus/). I found this one much easier to use than the Adafruit GPS library.