If your customer insists on framing the original newspaper, have him sign a disclaimer for discoloration, which will happen from almost any amount of light exposure. The disclaimer wouldn't save you in a lawsuit, but it will make the customer think twice.
You can frame a copy of the front page folded into another newspaper of the same size, and it would look about the same as the original. You will probably have to work on the edges, however, to make them newspaper-like.
Edie is right about the clear film mount. But instead of encapsulation, I suggest you make a two-piece Wrap Mount using an undersized, reinforced alphacellulose backer. If you need more detail let me know privately.