Hi Warren,
I think the package with the addon Argyle Airport is "grenadinesv2" and it's actually by Jean-Louis Valladier ( written as Valladier Jean-Louis at Avsim). He has modelled Argyle Airport, but as it was before it was opened, he called it TVSG.
It is a very simple fix to rename it as TVSA. First make sure you disable any other addons for that airport. Then download Airport Design Editor:
http://www.scruffyduck.org/downloads/4584110854 (Download the manual too)
Go through and set up the options which requires you to point to some files, and choose units of measurement etc.
You may need to have a SDK installed. You can download and install the P3D SDK(s) from the P3D site.
Open ADE in P3D V3 mode (If that's what you are using). Choose "Open airport from bgl" and then open the file "TVSG_ADEX_JLV.BGL".
Go to "Airport Properties".
Change the code of the airport from TVSG to TVSA.
Choose compile airport.
Change the name of the compiled file to "TVSA_ADEX_JLV.BGL" and place it in the Grenadines/Scenery folder. Turn off the file called "TVSG_ADEX_JLV.BGL" (eg TVSG_ADEX_JLV.BGL.OFF).
Change the name of the file called "TVSG_ADEX_JLV_CVX.bgl" to "TVSA_ADEX_JLV_CVX.bgl"
Now with this scenery activated the Argyle Airport will appear as TVSA.
Let me know if you have any problems. I have just tested this in a few minutes, so if you have trouble I will send you my files. I would rather show you how it's done though, as then you can do the same again any time you need. ADE really is pretty easy to use and an amazing tool.
Cheers,
Scott