Jambalaya- substituting chicken for shrimp?

That is way too long to cook the shrimp, anyway - usually it is added more towards the end, to prevent it from becoming tough and rubbery. (which it would, if you used shrimp and cooked it according to this recipe). If you add the chicken in the beginning, with the sausage, and cook the rest of the recipe as directed, your chicken will be fine! You are talking about bite-sized pieces, and by the end, including the browning stage, the chicken will have cooked 45 to 50 minutes - plenty of time!