I'd think you'd want to see what a good paper conservator would want to at least flatten and stabilize it.
Other than that, if it was mine what I would do would be to get it as flat as possible, I usually get it flat and place the area or item under some weight for a while. This doesn't always work, but on thin paper it usually helps. By a "while" I mean like a few months, checked maybe once a week. Some stuff flattens nicely in a day or two, some just doesn't.
Once it's as flat as it's going to get, I'd put it between a couple sheets of Mylar, and use a roller to squeeze the air out. This is NOT laminating, which melts the plastic together and onto the surface! Just using the smoothness of the mylar and air pressure to seal it in and hold it in place. Mylar is archival, so after that unless the paper is very acidic, you should be good for a couple hundred years
The mylar will hold the item in place, and protect it.
Now the mylar with the item inside can be matted as you wish. I might leave some room around the sides, so the whole item was visible. Although it might display a bit better with the torn edges covered up.
Steve B