There are three versions of shutoff valves commonly available: threaded (screw-on), compression (has a nut at the supply side), or soldered on. There is one other possibility, but probably not available when your house was built and that is a push on connection that uses o-rings to seal and grippers to hold it in place.
Once you determine what you have, your replacement options will become clear.
In all cases, you should be able to remove what you have and replace with a new valve in the finish you desire. Removal technique will differ, and you should not need to tear up the wall.