The config module is included with the GPS 175. It will be physically located in a special holder that is part of the metal backshell assembly of the large connector for the GPS unit. This module will contain all the uniqueness of the installation that you will program into the module at power- on time.
The Dynon ADHARS module provides altitude info to the Dynon transponder. I believe the Dynon install manule shows an example of the wiring for a Garmin GPS navigator using the a serial line and the -429 interface module.