Edit a User_comp .c file and utilize

So I have a GS20 vfd. It is the replacement for the old GS2 drive that the existing hal component exists for. I am only using it to pull vfd status, load %, current, voltage, and generate some user messages. I am using the 0-10v and fwd/rev start/stop physical pins from my mesa 7176e card.  I plan on adding an encoder for rigid tapping down the road so I want realtime spindle control rather than modbus.  All I want from modbus is some status messages and the ability to send a reset command.   I found the gs2_vfd.c file on the github repo, and I can verify that the modbus hex register locations have changed for the gs20 for some items and I would like to re-write this file for the gs20.

I have no problem editing the .c file, but my question is how do I utilize this file afterwords? Do I need to install the dev version of linuxcnc to have access to source files?