Did it shake above 60 with the old tires?
As mentioned, before firing the parts cannon at the car find someone local with a Hunter Elite road force balancer or equivalent and make sure they know how to use it in road force mode. It will quickly and inexpensively confirm or rule out a damaged wheel, defective tire, or poor balance job. You don't want to misdiagnose a suspension or steering issue and spend a bunch of money changing parts only to find it was a wheel/tire issue from the beginning. Several times a year I see cars with fairly new tires that look great but have internal tire defects that cause vibration or pulling, and a good operator on the Hunter can quickly find the issue.
As far as doing all the work yourself, get a 3 day subscription to AC Delco TDS or Alldata DIY and read the factory service instructions for each job on that estimate. If that steering rack is electric you probably can't swap it without an MDI interface and the factory GM GDS2 software as the rack may have to be flashed once installed and it will probably need a steering angle sensor relearn. Regarding the brakes, if the rear has an electronic parking brake you may need the factory software or a third party scanner to command a retract of the parking brake before swapping rotors and then reset them after the new rotors are installed. Always a good idea to read the service manual before diving in, especially on the newer stuff that often requires the factory diagnostic software or an expensive third party scanner for many procedures.
