1996 Mercury Sable Transmission and Odometer.

Transmission problem
1996 Mercury Sable 6 cyl Front Wheel Drive Automatic

My transmisson won't shift properly. I have to manual shift it from 2nd to drive and at times it wont shift right away so you have to run it in 2nd for awile then some times it does it seems after I am over 50mph it will work. I have changed the filter and it took care of the problem for a sort time maybe 2months. Also my odometer wont register most of the time just on rare occasions. Everything else works fine. Transmission shop told me to add a quart of Lucas and see if that helped it did not. They told me that they cant give me an estimate unless the break it down and it sounds like I need a new transmission. Very expensive. By the way pan had very little metal shavings. Any ideas on these questions? Please help.