I bought an eg hatch that has a gsr dash in it. What I'm wondering is how complicated it would be to replace the gsr dash with a stock one. Would i just need an OEM dash, cluster and wiring harness, or are there additional parts I'd need.

 

Safe bet you'll need the ENTIRE under-dash wiring harness. You'll also need the lower dash plastics, new door cards, and more than likely a new full HVAC unit - everything from the controls to the heater core. Someone put a metric shitload of work into making that dash work. I would just leave it as it is.