Well, if you don't have any experience involving UIFILEs, you'd better learn it first a little or simply stay away from it.
Luckily, the worst thing that can happen when you try to modify the skin would be that the skin won't loaded. Back in the days where skinning was done by modifying the files themselves, you could simply screw up the executable and start all over again if you didn't make any backups.
Well, it's up to you. Perhaps you should first try to contact the creator and in the meantime, experiment a bit with it if you have nothing else to do.
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