That's a pretty big request. You may want to purchase a character book or search on the web.

That said, you want to finish your modeling, unless you are happy with the spheres and cylinders. You do not need to convert to polys, in fact, for the bones, you may be better off with nurbs, since they are sweeping shapes. I don't know why you would want to combine shapes if you used polys - you'd want to keep the individual bones separate for rigging.

However, you should do your modeling in a standard, standing pose. Modeling against a bent up drawing like that will only get you in trouble with sizing, and then the rigging will be easier if you actually have everything in the right place. You don't want to rig crunched up like that.

When your model is done, you will create "bones" to represent the skeleton for your character. Since all these shapes are "hard" - ie there is no skin to fold, or anything, you will have it easy. All you will need to do is group your bone geometry under the "bones", and then as you rotate the "bones" of your rig, your geometry will follow along. If you model it like a real skeleton, you can make a jaw bone that you can rig separately from the cranium that you can use to make him speak.

So the lesson today, is start a little bit easier if you are attacking the entire picture, until you get a better idea of what you are doing.