How to Script GTA 5 - Absolute Beginners
Finally someone went well beyond the trouble of creating the best, most complete/comprehensive, easy to follow, tutorial to learn how to script GTA 5. There are two sections, one for absolute beginners as well as a more advanced section. You will learn how to create your own mod menu with LemonUI, as good as any professional programmer, and learn many cool tricks in the process like setting wanted levels, spawning cars, and weapons stuff.
You can read more here:
NucleiLite Wiki (this is the name of the project, which includes the source code for a fully functional LemonUI mod menu).