I think I have bitten off more than I can chew. My plan was to have a GPS driven nixie speedometer for my old Beetle.
I bought all the components I think I will need, but I haven't the slightest on how to make it all work.
The parts I have:
NEO6M GPS unit
Arduinix V3
Arduino UNO
Nixie tubes and sockets
Voltage regulator 12v to 5v
You'll need some specialized circuitry for the nixie tubes - they want about 70 volts to work properly. Consider a 7 segment LED display instead - it'll run fine off 5 volts, and it's almost as retro as the nixies.
Of course, there are lots of examples in the library. It's also available from the Arduino IDE Library Manager, under the menu Sketch -> Include Library -> Manage Libraries.
You should also be careful about the serial interface to the GPS:
Software-wise, use AltSoftSerial if pins 8 & 9 are available. If not, use my NeoSWSerial library. It works on any two pins. There is no reason for you to use SoftwareSerial. It is very inefficient, and it can interfere with other parts of your sketch.
Electrically, the NEO-6M is a 3.3V device, so you have to shift the 5V levels of the Arduino. A level-shifting module is best, but there are other ways to do it with a few discreet parts. You usually connect 5V to the GPS module's VCC pin, because it has an on-board regulator that converts 5V to 3.3V, to power to the GPS chip. Be sure to verify what voltage the GPS VCC pin needs.