Installation: everything in the txd folder in gta3.img needs to be replaced in gta3.img everything in txd in models needs to be replaced in the models folder with the game.
txd in gta3.img contains all weapon textures in the game, with the replaced icon in txd in models lies txd on thin, where the fist icon, map ring and sight are replaced.
If you don't want to replace files, there is a ready folder where png images are located.
All icons are renderings of models with a superimposed gradient. I did it for myself, but because they are "gathering dust", and the mod is actually ready, I decided to post it