- No. JOGL is a wrapper library for OpenGL, which means it simply gives you access to the OpenGL api. So whether or not you use JOGL, you still have to know and use the OpenGL methods.
- Greenlight supports jar files, I believe Windows Marketplace doesn't, as it's only for apps.
One benefit of using JOGL or LWJGL is that it gives you access to helpful classes like classes for spritesheets, textures, images, rendering, keyboard / mouse input etc. But that way you don't actually learn OpenGL like you should. It is an option though.
But yeah, switching from XNA to OpenGL might me a struggle. XNA is designed mostly for students (and very easy to use so everyone can make games with it after a little research). With XNA you use XNA render features, but in OpenGL you have to do everything yourself.