I'd start with updating your game to 18.104.22.168. after that make sure you have OpenIV or SparkIV (but it's best to have them both).
Those programs are for installing weapons, player items and player models but if you want to install some scripts like you say make sure you have an asiloader and scripthook. There are various asiloaders out there, but to make this as easy as possible just download this (files meant for patch 22.214.171.124. so make sure you got that first):
It's the simple native trainer with all required files (these files are required for any scriptmod, so if you have them you never need to download them again). You can leave out the trainer.ini and trainer.asi files if you don't want simple native trainer but Id recommend installing it because it's very usefull. It's for spawning cars, changing into different player models, changing clothes/weapons etc etc. Very useful and makes the game alot more fun. To launch it simply press F3 ingame (then use numpad to scroll through).
Just let me know if you run into any problems and I'll try to help you as best as I can