Rack and pinion replacement?

If yours has the electronic power steering instead of the hydraulics yes it needs to have the steering module reprogrammed when the rack is replaced. It's possible to use a used one, but it takes some special electronics gear that only a few people have. Plus, with a used unit you don't know what other issues you may have. To program it you need the proper software on a scan tool or laptop that can access the steering module. Because there are multiple scan tools and software with and without that ability it would be hard to say if your local shop can do it. However, a GM dealer will have the proper tools, but likely cost more.