mustang gt 2000

Hey. I am just starting on here. I have a major issue with stang and do not know what to do. The Transmission is shifting into all gears, but is not wanting to shift into Drive. Just had the rear-end rebuilt, by a Ford Mustang Professional. I really do not know what is causing this. Please help.

so the other day my intake manifold cracked and leaked coolant so i replaced it yesterday with a pi manifold and everything was good for a bit until i started driving it to my friends house the "service engine soon" light came on and it was shaking alot so we used my friends tuner to see what...