Welcome you "Newbie"
In order to get GTA V Models in any kind of 3D software (.obj or .fbx), you'll need the following tools:
Exporting the Model and Textures in openFormats
3ds Max 2017 & GIMS Evo
An GTA V Modding Suit only exists for 3ds Max 2017 under the name GIMS Evo.
You can get a student license of the newest 3ds Max. Getting 3ds Max & GIMS Evo on the other hand is a bit tricky to get.
Inside 3ds Max
If you got that far, you can import it and follow the instructions, its very easy.
Or just search up YouTube Tutorials, as they might be more informative.
Once imported, you could export it, which might work (Never tried yet).
There are forum threads, giving you the Modding Suit, but some work some don't or are bugged...
If you got all the stuff, feel free to DM me and I'll help you finding the right GIMS Version.
3ds Max might get tricky also, I'm unsure if there's GIMS for the newest Max version.
Best regards, Rach'