Hello
Theres a cable which runs to the Trannie and puts it in to gear. Check to see if that cable isnt broken. IF the cable is good and you see the linkage moving then its possible you need a trannie rebuild. Sometimes replacing the fluid will give you a couple more miles. Trans fluid needs to be changed EVERY 15,000-20,000 miles for long life. I dont know how long you have had your car but if you havent done it in a long time it needs to be done. Yes the cradle has to come down to change the trannie.