They wont be able to tell if the rack is bad if it is internal, which it likely is.
For the rack you just need to verify if you have magnasteer or not. You can crawl under the car to see if you have a plug in, or you can check your RPO codes. The sticker is in the trunk under the panel that covers the spare tire.
Replacing it isn't super difficult. The only "specialty" tool you need to make sure you have is a 18mm line wrench.
#1 Jack up car, support with jack stands under the frame, and take off tires.
#2 Pop tie rods out, and some people recommend unbolting sway bar end links.
#3 Place jack under rear of subframe and unbolt rear 2 rear subframe mount bolts.
#4 Lower subframe about 2 inches to gain access to mount bolts and line nuts
#5 Using the line wrench remove the power steering lines from the rack.
#6 I don't recall the size of the mount bolts but I am thinking its 18mm. I know the nut on the backside of the bolt is, but can't remember if the head is larger.
#7 At this point you should be able to start maneuvering the rack out. (If it is magnasteer don't forget to unplug it first)
That's the basics. There is a really good video on YouTube that I watched to verify some things before I started.
