Here is my experience with this airport.
I downloaded the file from Flightsim.com along with several WoAI packages that serve ZGGG.
Following the install instructions and without editing any flightplans I see...

I spotted for a while and AI departures and arrivals all worked OK.
You do not need to edit any flightplans if the airport is installed correctly.
AI will use the ICAO code regardless of the lat/lon listed in the airports*.txt portion of the flightplan.
The purpose of disabling the default files is to remove all reference of ZGGG to the default airport.
If you do not see what I posted in the screenie in the Go-to-Airport window, if selecting (new) takes you to the old airport, if you see AI at the old airport, then I think that you do not have this airport installed correctly.
You might have a corrupt download and need to delete what you have and download again.
Also, any edits you make to traffic030528.bgl will impact that file only and not change anything in any other flightplan.
Hope this helps.
cheers,
Joe
Don't argue with idiots, they drag you down to their level and beat you with experience.