The wiring given in post #2 is pretty much correct*.
Before slicing off the XLR5 connector, open it up (if its not a molded connector) and note which wires go to which pins. If it's a molded connector, leaving enough cable to go back (if necessary) strip back the outer cable jacket. Then, one at a time, cut each inner wire and use a continuity tester to see which wire goes to which pin. Make sure you can uniquely identify each wire.
Use the continuity tester on the GA plugs as well. Getting the correct functions (mic+, mic-, etc.) connected to the correct GA plug positions is more important than color codes.
*On some headsets, DC is supplied to noise canceling electronics. The DC+ is connected to the XLR5 pin 5 (otherwise not connected). On the GA mic plug, the plug tip is DC+ (otherwise not connected).