speedometer on my 93 merc sable is sticking at zero when accelerating slowing the transmission shifting- is this an easy fix ?

A non working Speedometer should NOT have any effect on the way your transmission shifts gears, especially on a 93. Your shifting problem is most likely a failing transmission or some type of sensor or sticking valve/solenoid in the transmission. As for the speedo being stuck on ZERO, that is probably a broken end on the cable that runs from the trans to the dashboard. They have a tendency to fail at the transmission end where a plastic gear with teeth that attaches to the cable and is driven inside the transmission. The gear could have snapped off or the teeth could be worn down. Have you taken the car to an auto parts store and have them check for any trouble codes?