Hi Vince,

1) What do you mean by Reset Pivot? Do you mean Center Pivot? It's under Modify.

2) If you click on an object in a group, you can press the up arrow key to select its parent.

3) Normal mapping can add small details without increasing the poly count. A normal map is a cheat, as it doesn't actually modify the vertex positions - it modifies the surface normals per pixel. Normals are what are used to calculate how much light that face, or vertex, reflects. If you modify the normals with a texture, you can simulate more geometry than there actually is. This effect breaks down however, as noted previously it does not actually modify the geometry. This is an issue when you look at a face at a grazing angle, or create a feature that is too large. For example, take a look here: Normal map example with scene and result. As you can see the effect breaks down for large objects, and for grazing angles. If you looked at that plane from the top, it would look identical.

4) What do you mean by "your grid is 12 units"? Are you using the default grid settings? Then each grid square is 1 cm, and each value in your channel box is 1 cm as well. The default grid is actually 24 square centimeters, as it is -12 cm in one direction, and 12 cm in the other. I have no idea why your settings would have those values, but it is not related to the scale.

5) Select both objects and go to Edit>Delete History. The reason why it is behaving like this, is because Maya has a history, which defines how an object should be operated on. In your case, the mesh has that curve extrusion in its history. If you delete, or modify, the curve, the extrusion in the history will not be able to find that curve, and will fail (making the mesh disappear) By deleting the history, you "bake" the history down to the actual object. You should always do this when you are happy with the look of an object, as it reduces file size, increases the speed of your viewport, and eliminates some errors, such as the one you are currently experiencing. However, be careful when you do this, as there is no going back (Besides undoing), so make sure you do not need the history before you do this.

Hope this helps, and it's looking good!