A few questions on skinning

Well I have learned how to reskin the materials for various source games and how to import them into a skin, but I still have a few minor questions:

*If I’m making a skin and I rename the files, will they still work?
*Is it possible to get rid of some of the things without messing up the skin? Because I’m making a personal skin using the citizen sheet, but all of the useless stuff around it is in the way.
*How good does the shading have to be? Because I have seen good reskins that seems to have no shading at all, and yet when I just recolor something without shading it seems to me like it would look like shit.

Answers to any of these questions would be very helpful. Thanks in advance.