If the ring gear is clean (the pinion as well) other than the bolts and the holes in the carrier ain't wallowed, you can re-bolt the ring gear up and run a picture to check contact. If there is damage to the carrier, you will have to replace it. This means resetting the picture by changing the backlash. If the ring gear is damaged and you need to replace it, you will have to replace the pinion as well. This will entail resetting the pinion depth as well as the backlash. A job best left to the experts.