Gear wont change in auto Lebaron GTC 1995

Hi Guys,

I have a Chrysler Lebaron GTC 1995 model. It was working fine until i
got it inspected. The guy was trying to fix the reverse lights in the
rear and eventually when i went to pick up the car the following
happened:

1. The speedometer not working

2. The gear not shifting. I can change it to all gears like D, 3, L R
P etc etc. But whatever gear i put in, it does not shift from 1 to 2
or later. It stays in gear 1, no matter if i am D, L, 3. Everything
else is ok. The mechanic said it was speed sensor relay and he
replaced it. But that doesnt work. Now he is not sure himself. Any
help will be appreciated. Also if someone can tell me how to find the
detailed guide to repairing this car, that would be great. Many Thanks

AG.