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I don't know how to make a skin changer but others have released their assets for SWBF1. SWBF2 is usually very similar. I'm not familiar with x.lvl file.
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Look in Sleepkiller's assets, and/or use the search function to find forum posts. There was a lot of work on it back in the day.
And when people don't answer your posts, it is because we don't have any information for you. Although we encourage SWBF2 modding, we don't have as many SWBF2 experts here. Gametoast is a good SWBF2 source.
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