This mod replaces niko's standard outfit with guppe sechs security uniform.
install:
1.Drag all the files(EXCEPT "player_p.wdd" and "player_p.wtd") in GrandTheftAutoIV/pc/models/cdimages/playerped.rpf,
2.Drag "player_p.wdd" and "player_p.wtd" in GrandTheftAutoIV/pc/models/cdimages/pedprops.img,
you can use the latest OpenIV to open that .rpf & .img file.