This video shows you how to install it.
Here are some of the functions of the mod:
Improve your weapons
Up or down your wanted level.
Download it from here.
There are different options, but here I have listed only the best ones:
Have fun with unlimited money.
Get all weapons by the start of the game and make your ammo explosive and infinite.
Turn into animals.
The mod is 100% legal, but it is not allowed to be used in the online mode!