I want to make renders but I'm not very good at blender and I'm having trouble opening the .gltf for the render
why would you ask that here. also you know you can actually use a really cool thing called google its a very new concept
I think you just press f11, or open the Render tab up there and click on Render, if it is what you asked.
To open the gltf file you go File -> Import -> glTF As for actually rendering it, there should be plenty of tutorials on youtube on how to render it or at least some guides that can help start you off with learning how to render.
Does anyone here know how to unpack the official beamng vehicles so top they can be altered in blender? Sorry for off topic
copy a dae file to mods/unpacked/folder/vehicles/vehiclename/, then in blender, to import>collada (.dae) and select the file, then once you export it, the parts in there will overwrite the vanilla ones if they have the same name.