What I want to do now is to interface the mega with my Pixhawk flight ... This is step one which as a beginner with arduino became quite an obstacle, due stictly to the crappy documentation of this ...

This project connects a 16x2 or 20x4 LCD Display to an Elegoo Mega 2560, allowing it to display messages or real-time data. The project supports both I2C communication (recommended for fewer wires) ...