He's a mid-rotation pitcher, both on performance and ratings. Therefore, my guess is that you could replace him for about the same, although it will vary world to world and season to season. I'd roll the dice, not sign him yet, and see if he'll re-sign for fewer seasons after rollover, although I'd expect the same dollar demand. If he refuses to re-sign it probably won't be a big loss.
If you do sign him for 5 seasons you will want to create a back-loaded mutual option, since by 37 he probably won't be worth it.