I've done a whole chicken in my crockpot, but not with dressing inside. I found that when the chicken is done, there's a lot of chicken fat in the bottom of the crockpot. Because of that, I'd do my stuffing separately. But you have nothing to lose by trying!
I make ziti in the crockpot for family get togethers. Reserves my oven for other things on busy days...like home made bread!