Some screenshots ^^:
#1-Get SparkIV or OpenIV and start it.
#2-Browse to your Rockstar Games/Grand Theft Auto IV/pc/models/cdimages and open "playerped.rtf".
#3-Replace the "uppr_diff_001_b_uni" there, by the one that I provided you with.
#4-Save everything and start GTA IV.
NOTE - DONT FORGET TO BACKUP