Oh, one thing I noticed reading the thread... Looks like you're assuming a certain directory for EQ2... Well, you can eliminate this little assumption simply by looking in the registry for the full path to your EQ2 main executable.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\Everquest2.exe
has two values... default value, which is the full path and the executable name, and Path, which is just the path. As for the location of the files to update... Well, you can use the path variable to find their eq2.ini file... which will tell you what the folder name for their UI happens to be... Maybe put an option in there to say "always update current UI", or allow them to specify which UI they want to update... default to the current one... Save that info to the registry... What all THAT would do is allow you to run the program from ANYwhere and actually find its way to where it needs to be. Anyway, ideas, ideas, ideas.
Let me know if you need any help with that stuff, I might be able to find stuff for ya.