w/ XNA's basic effect class though you probably won't be able to get your vertex paint working in 'engine'. You or your coder will need write an .fx shader to use or maybe checkout shaderFX and see if you can't make something that will work. I'm pretty sure it an export to XNA as wel. Once you have a shader though, you'll…
Yes, if whoever is coding your app knows how to get it done. You can do whatever you like. If you want vertex painting, get the programmer to write the proper rendering technique. XNA is not an engine. It's a framework/wrapper around Direct3D9 for C#. The phrase, "how do I texture for an XNA level" doesn't compute. You'll…