Metal restoration can be anything from covering a simple scratch or bad spot and for these I use Brownell's Oxpho-Blue. For larger areas I am set up to rust blue anything up to the size of an action.
The most common unwanted (IMO) conversion is the mounting of a modern scope. The receiver is drilled and tapped, the bolt handle is then bent and notch is cut in the stock and many times into the action itself.
This work in beyond my abilities and must be sent out. This is not something to be undertaken by an amateur.
Here is a rifle that had all of that done to it. Only the area where the wood was replaced was refinished, the rest of the rifle was not.
http://img.photobucket.com/albums/v311/mjpetrov/jw8.jpg http://img.photobucket.com/albums/v311/mjpetrov/jw13.jpg 
