Air carrier First Officer reported distraction when Captain dialed wrong descent altitude in attitude select resulted in premature descent.

Narrative

We were arriving to MCI with the airport in sight and were just North East of the final approach course. We were cleared for the visual approach to 19L and began the descent for the Final Approach Fix (2;700 feet). I looked to my right to clear final; as well as to review the chart one more time; and when I looked back we were descending through 2;000 feet. When I looked at the altitude window I saw the CA had accidentally set 1;700 instead of 2;700. We had just descended through 1;000 feet AGL before the Captain could push 'ALT Hold'. We climbed back up to 1;000 feet AGL and continued the approach and landed uneventfully. We were back at 1;000 feet AGL prior to the FAF so we felt it was OK to continue on the visual approach to the runway. Cause: It was an early morning for both of us (we talked about that with the threat brief); this was also the third leg of the day with roughly 6:30 of flying being done. Suggestions: Had I been more aware; or realized that the incorrect altitude was set earlier; I could have said something sooner.