Well, I can share you the tools I used for making this. :-)

URL removed by steam. Well I don't want to 'go around' this problem by just making the URL invalid so I'll just PM it to you.

Lets hope steam does not block that URL.

On top of those tools I suggest you install 'assimp viewer', it has free utilities for converting various model formats to other model formats. So with it I did fbx -> .obj/.mtl conversion.

So with the GRF editor just export the GND and RSW files, then use the ROMAPCONV1.9 tool to convert that to FBX model with textures and uv-coordinates.

The only thing I had issues with were the normal vectors of surfaces. I tried to fix them easily in blender but couldn't figure out a way that wouldn't take ages. So as you may have noticed, in my VR conversion of Prontera the surface normals are pointing in wrong directions in most places, lighting looks okay but if I'd build a lightmap the surfaces would have dark artifacts, etc.