Hello there. Could anyone tell me if there is a way to add clothes to the game as add-on, whitout replacing anything?

Hello there. I'd like to ask if anyone could tell me how to modify modded cars, since some of them have some bugs or problems (like lights not projecting any lightray in front of them or having to make a new texture since the original one has some problem).
Could anyone tell me how to modify every single part of those files?

Does anyone know how to add or remove the siren on a vehicle? Can i just remove the sound but keep the lights? What should I edit?
Thanks to everyone who's gonna answer.

Hello everyone. I hope this is the right section to ask.
I'm new in the modding world and I'm looking for a helicoper to add to a fivem server. I finally have found one which is pretty good but it has more than one texture or "aspect" (idk how to call that). I need just one of those. Do you know what I should edit in order to make the game spawn always the same aspect?
Here's the mod:
https://www.gta5-mods.com/vehicles/augustawestland-aw139-lafd-westpac-uk-spain-add-on