1999 Plymouth Van Neutral Safety Switch

I was driving home Tuesday and my "service engine soon" light came on. I stopped at a local Auto Parts store to buy anti-freeze. When I attempted to re-start my car it would not start. The shop diagnosed the problem and said my neutral safety switch was bad. I was initially told it would take one hour to replace, I was later told 3 hours. I am now being told my selector shaft has some groves on it and will need to be replaced.
The repair cost are currently $600.00. My car has been in the shop for 3 days now.
How can I tell if I need this additional part (selector shaft).