Step #1: Download "IMG Tool 2.0" if you havent already http://www.gtagarage.com/mods/show.php?id=63
Step #2: Open Up "IMG Tool 2.0" and click file the click open and search for you gta sa directory.
C:\Users\"Your Username"\ProgramFiles\GTA San Andreas
Step #3: Once inside your gta sa directory go to models and click on gta3 to open it up.
Step #4: Then click edit and then click find and search micro_uzi.txd exactly like that.
Step #5: After that click on commands and click on replace browse for the folder where you extracted
Step #6: Then click on commands and click on "Rebuild Archive".
And your done! Have fun with your new golden uzi!