So a little history first, this is my son's car, it's a 2000 Park Avenue 3800 supercharged. This car was originally having issues going into park and if you put it down into 3rd it would get stuck and you would have to get underneath the car and force it back to park because the shifter wouldn't move at least that's how he explained it to me. I told him it sounded like the transmission range selector that the shift cable hooks to. He had a friend mess with it and get it to where it would go into park and he just didn't shift into the manual gears below D anymore and it was ok for a but then all of a sudden it stayed in 1st gear and is stuck in limp mode. He said the shifter still didn't feel right going into D so i'm wondering if that range selector switch can cause it to go into limp mode? It does have a code for a speed sensor which i'm sure can cause it. The transmission that is in it is from a 2003 Regal 3.8 SC. 1st question is where is the range switch located? I have always seen them bolted to the tranny but a local repair shop told him it was inside the transmission and the whole K frame had to come off then the transmission pan etc. Sounds like maybe they were just trying to rip him off? Before I go there to look at it I wanted to get more info. Also is the speed sensor located near the front wheel hub like an abs sensor would be? Any advice would be appreciated so I can be more prepared when I over there to help him with it.

thanks in advance