there is short tutorial how to make Large signal modification on RGO ONE transceiver by Chris, G7DDN...
1. Remove top cover and disconnect speaker
2. Remove fan assembly - 2 screws on each side of heatsink
3. Remove two screws holding shield to rear panel - accessed through the heatsink
4. Remove 2 sunken screws in the side panels holding the shield in place to the chassis
5. Remove 2 screws through the PCB holding the shield to the PCB
After that follow the procedure which I posted over here: