Blender 2.71 baking

Hi colleagues,
I have an object built from around 10 materials. Several parts from this object are unwrapped for their textures. Because this object will be used in a game engine it will be better if it has only one texture with baked materials, lights and shadows … etc. How can I unwrap the object for new texture, for baking? At the same time I need UV maps for the parts which has input textures …

Is there more advanced tutorials for texture baking? In the Internet i found 2-3 tutorials but they are too simple …

I managed to do it with simple cube and plane but it is so slow for advanced meshes …