I assume that you are referring specifically to the replacement of the 1st carpometacarpal joint.
After such a replacement is done, you can expect a better quality of life. Pain should be eliminated almost immediately, and joint motion will improve with the presence of the new joint. Certainly, the pinch strength of the thumb after replacement will not match that of a completely normal thumb, although it will be stronger than what it is before surgery.
The ability to play musical instruments, using the computer and mobile devices will post-surgery.