In order to get to the speedo you must pull the instrument cluster.
In order to pull the instrument cluster it is best to disconnect the speedo cable on the back of speedo.
The instrument cluster is held into the dash by friction. There are tools that you can buy or make yourself. The tools are basically wires with T-handles on one end and little L hooks on the other. The L hooks slide between the instrument cluster and the dash.
Please see this thread:
Remove Instrument Cluster
Also see this threads:
Many Instrument Cluster Removal threads
Haasman