I’m not the best qualified to answer this… But I’ll get things started. A lot depends on the game style you’re planning. In your shoes I probably wouldn’t rush to make actual models yet. Try and tweak or customize existing assets instead. The main reason is, creating low poly meshes is one thing, making high-poly skelmesh / rigged vehicles is another… Its a huge divide… Arguably greater than going from nothing to Blueprint Scripter / basic coder etc. With 3D there’s more risk of f’ing things up (but in less obvious ways imo)…
Anyway, pick your toolkit for textures and modelling… Photoshop or Gimp or equivalent for textures etc, 3D app for modelling etc etc. Start by dropping what you don’t need. 3ds Max is prohibitively expensive, so I’d avoid it. Also try to avoid traditionally high-poly sculpting apps such as Zbrush for now anyway. Instead look to Houdini / Modo / Blender / Maya LT etc… Download trial versions and see which you like. Personally, I’d go with open-source i.e. Blender. Start from Blender 2.8 on… Last I read, release builds were coming first / second QTR 2019. As regards modeling and tutorials. It comes down to personality. Once you’ve picked a 3D app, search for threads on here with your chosen app name in the title, to find links to favorable courses.
Overall, in your situation though, I’d consider a slightly different approach. Such as bartering your coding skills in exchange for models. Start working with a skilled modeler. Shadowing them as they go about creating models for your game… I just think it will be quicker, and you’ll encounter less mistakes / experience fewer dead-ends in the end.
I’ll leave you with one last thought… There are very few supermen on here… Brilliant coders that have managed to combine coding and being wonderfully talented at modeling as well. Its just rare. As they’re two different very specialist skills. So be sure that’s the right move for you and your game… Both will eat into precious time that may be better spent on improving Gameplay etc… Just 2c… Good luck!