Importing with textures

That grey material is Maya's default shader. You don't see the textures applied on the model cause most probably they haven't been embedded in the exports ( 3ds as far as i know doesn't have the embed texture option). Anyway, if the package contains the textures separately , it shouldn't be a problem, you can easily assign them to your mesh. Also i'm not using Maya, but it possible that for the ones that have embedded textures, the material itself has some kind of option like in 3ds max "show material in viewport" ?

It depends on the situation, you could have a simple model with a single material ID and a single diffuse and that should work with just&drop on the model or maybe you have a multi/sub-object material and lots of material ID and this may be a bit more time consuming if you don't know what goes/where. It also depends on the renderer, if you need it for a game engine or not. Most probably you'll have the setup all the inputs like albedo/normal/AO/roughness/metallic (depending on the pipeline). But btw if you have the textures inside the package, it's not the same as re-texturing the whole model, rather just re-assigning material job, which shouldn't take long. I don't know how to further assist you without better knowing the situation unfortunately :P

from my experience usually only color (diffuse) texture shows properly from fbx and obj/mtl... (in maya / max / unity)
If you export fbx with material and open fbx in text editor i find the reference to other textures as well, but no importer i tried respects that...
so no solution for you, just saying i have same issues with fbx : )