Schedule changes are a pretty common occurence. Especially on a reservation booked nearly a year in advance. The reason CO didnt call is that most airlines will generally wait until much closer to departure to avoid repeat calls due to multiple changes. I believe unless its a major schedule disruption, they call approximately 3 weeks out.

There should also be no reason to reissue the tickets unless your connection cities have changed.

As for the exit row..perhaps the seats had already been assigned and there just wasnt room?