Turkey Dressing Question

I have a de-boned turkey breast stuffing question to ask the pros. I want to lay the turkey breast open and lay my favorite stuffing in it. then i would like to add bits of italian sausage on top of the stuffing. then use cooking string to seal it up and put it on my Traeger grill until internal temp hits about 160 degrees.
My question is this. When adding my sausage do I add it raw or pre-cooked?
Also–is 160 internal temperature ok or should I go higher?
thanks a bunch!!

thank you very much. yes i will have fresh uncooked turkey breast and will add uncooked stuffing and uncooked italian sausage then secure it with string and cook on my Traeger grill till internal temp is 170 degrees. Correct?