Yes, if you re using an external antenna it would be easy. If you are using the internal antenna, it may effect the signal strength if it is facing down.
You can also use the spare pin holes to provide 3v and us TX/RX to get the NMEA sentences.
If i’m mounting it upside down, I’m going to assume that I will either need to build a connector for it or is there something on the board I can do and use the connector that comes with it?
In the image above, the pins you can use are highlighted in the red square. You can solder some pin headers to these and then use jumper cables to connect it to your Raspberry Pi. There is a description just below the pins of what pin is what.