UV Wrapping and Baking into UE4 Steps?

Yes, the UV mapping is what allows you to take a 2D image and place it on the 3D model, so you can do the diffuse map at any time as long as you have your UV mapping set up. Note that if you change your UV’s then your textures won’t match anymore. There’s ways to fix that though–for example, UV’s have a channel so that you can have multiple UV sets–so if you wanted to change the UV’s and update the textures to match the new UV’s then you could put the new UV’s on the second UV channel and in 3ds Max you can choose what UV channel you want to be the destination of the bake, so the texture would be set to render with the first UV channel but bake to the second.