Hi zellfy,
So let me see if I understand this correctly. You want to replace the usfont_XX.tex files with chinese characters ? May I recomend you to use the old 1998 version ? Using it you can easily insert direct *.png files into the game (instead of *.tex files) plus, the resolution is 4 times higher.
In any case you need to extract the original usfont_XX.tex files and drag rulers for rows and columns on top for each character with either photoshop or gimp, and then draw or write your own characters.