I need help with my 2005 mustang

In late Nov. I went on a nine hour road trip, twards the end of the trip my speed-o- just quit. Once I got home I disconected the batt. to try re-set the computer. It worked, although the speed-o- works to well now. After driving even a little ways the needle will get stuck anywhere from 5-20 MPH. What can I do to fix this problem without sending the car off?:crying:

Remove the cluster and have the speedometer sent off, or replace it.