If, the head is not cracked then a welder and a grinder would probably do the trick. Only problem if you weld it the head could warp. After welding I would check the head for straitness.
I would just blend the area where the piece broke off. and take the sharp edge off the chambers. Ive seen worse and the heads were still salvageable. Might want to check your turbine to see if that piece may have hit it .