You sure have lots of questions!
1. Lock all the layers you do not wish to copy to another file;
2. Make sure none of the layers (and contents) you do wish to move are locked;
3. Ctrl-A Ctrl-C (Select All, Copy);
4. Create (or open) the file you want to copy into;
5. In the layers palette, click the little flyout menu arrow (top right corner), and go most of the way down the list, check the option called "Paste Remembers Layers";
6. NOW it's time to Ctrl-F (Paste in Front), and watch all the art appear in the original layer configuration. If you do Ctrl-V (Paste) instead, the contents will not land on the original coordinates;
7. Good idea to turn off the Paste Remembers Layers option after you're done, otherwise you will have trouble down the road trying to paste back and forth inside the file.