Most of it, not all. There are specific assisted tours. Call in advance to be wise.
Yes I believe the shrine is accessible and there are indeed people to provide assistance.
Is the person driving there? Or are they going by train? I am not certain all the trains are accessible, th person may want to confirm prior to planning the trip.
Yes, I too believe I saw people with wheelchairs. There are sections of the area that may not be accessable, however they may have elevators to accommodate those that require it.
The area is very large and a lot to see.
Get quick answers from Our Lady of Czestochowa / The Black Madonna staff and past visitors.