Transmission on 1991 Acura Legend

D4 light flashs and speedometer falls to zero miles per hour
than back up to speed.

2 answers 1 comment
The D$ light flashing indicates an automatic transmission fault but yo are lucky in that the Vehicle Speed Sensor (VSS) is a key sensor input for transmission controls. It operates the speedometer and is necessary fro cruise control as well. Common failure relatively easy to change and relatively inexpensive part (compared to a transmission failure).
my car is doing the samething the D4 light is flashing and speedo problems and from reading all the information I think its the VSS, my question is can I do it myself and what else should be done at the same time. Thank you.
my legend unless up to high speed will not switch gears ....also will not go into gear unless in neutral first