I've made a board that makes this project particularly easy - it's the SkyTraq Venus838LPx-T breakout board product I sell on Tindie, but there's a new variant designed to be placed over the first 12 pins of the Raspberry Pi GPIO header. It connects the serial GPS pins up to the two serial pins of the Pi, and PPS to GPIO 18 (pin 12). The GPS module gets power from the 3.3 volt supply, and the 5 volt supply is used to provide active antenna power with an AP2331 to protect from shorts and overcurrent.
This board plays nicely with any Raspberry Pi, but it plays particularly nicely with my Pi Zero W desk clock. If you use long pins on the GPIO header, knock out the GPIO cover on the case and stick this board on, you can follow the setup instructions here and on the Pi Zero W clock project and you wind up with a Stratum 1 NTP server that also has an accurate LED clock display. This combination, in fact, is ntp2 . kfu . com, which is part of the global NTP pool.
If you have one of my GPS Disciplined Oscillators, then this board will let you hook the diagnostic port of your GPSDO up to your Pi to make an NTP server. In fact, as soon as I get the board back from OSHPark, one of my Pi Zero W clocks with this board being fed from my lab GPSDO will be ntp1 . kfu . com.