start by checking your front end for wear in the tierods and all other linkage. the I would suspect your steering box is shot.
A locked steering wheel can be repaired by a locksmith or a car dealer.
you need to buy a steering wheel. {Cheap at auto part store} remove your horn cover screws from behind the steering wheel. attach the pully, screw it in and it will pull the wheel off.
yes
Try jiggling the steering wheel as you turn the key. Once the key is turned there is nothing left that locks the steering wheel so if you still cannot turn the wheel the problem is probably in the steering gear. Any halfway decent mechanic can repair it.
10 inches
most likely bad balljoints
It is likely underneath the plastic shrowd, just to the right of the steering column as you look at the steering wheel.
The size of the steering wheel on 2002 Impala is AXX. You can visit a local repair shop to learn more about sizing of steering wheels.
10 inches
Find out where the wear is in the steering linkage. Idler arm and tie rod ends most likely.
14 inches
In the steering column. You'll have to remove the steering wheel with a steering wheel puller tool. This can be a dangerous repair job due to the airbag in the steering wheel. Get a Haynes or Chilton's manual for the details on how to do this as well as how to disarm the airbag system.