Hello 
hope you have (IMGTool.exe) if you don't i have included it in the folder

open imgtool and go to (models) folder in your gta files and look for gta3.img then openit with the imgtool
after you add the files in you in the (import to gta3.img) folder then rebuild your img
After that copy the data folder to your gta vice city directour and replace whatever it asks you to replace

enjoy